1
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Ganjam S, Wang Y, Lu Y, Banerjee A, Lei CU, Krayzman L, Kisslinger K, Zhou C, Li R, Jia Y, Liu M, Frunzio L, Schoelkopf RJ. Surpassing millisecond coherence in on chip superconducting quantum memories by optimizing materials and circuit design. Nat Commun 2024; 15:3687. [PMID: 38693124 PMCID: PMC11063213 DOI: 10.1038/s41467-024-47857-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2023] [Accepted: 04/12/2024] [Indexed: 05/03/2024] Open
Abstract
The performance of superconducting quantum circuits for quantum computing has advanced tremendously in recent decades; however, a comprehensive understanding of relaxation mechanisms does not yet exist. In this work, we utilize a multimode approach to characterizing energy losses in superconducting quantum circuits, with the goals of predicting device performance and improving coherence through materials, process, and circuit design optimization. Using this approach, we measure significant reductions in surface and bulk dielectric losses by employing a tantalum-based materials platform and annealed sapphire substrates. With this knowledge we predict the relaxation times of aluminum- and tantalum-based transmon qubits, and find that they are consistent with experimental results. We additionally optimize device geometry to maximize coherence within a coaxial tunnel architecture, and realize on-chip quantum memories with single-photon Ramsey times of 2.0 - 2.7 ms, limited by their energy relaxation times of 1.0 - 1.4 ms. These results demonstrate an advancement towards a more modular and compact coaxial circuit architecture for bosonic qubits with reproducibly high coherence.
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Affiliation(s)
- Suhas Ganjam
- Departments of Applied Physics and Physics, Yale University, New Haven, 06511, CT, USA.
- Yale Quantum Institute, Yale University, New Haven, 06511, CT, USA.
| | - Yanhao Wang
- Departments of Applied Physics and Physics, Yale University, New Haven, 06511, CT, USA
- Yale Quantum Institute, Yale University, New Haven, 06511, CT, USA
| | - Yao Lu
- Departments of Applied Physics and Physics, Yale University, New Haven, 06511, CT, USA
- Yale Quantum Institute, Yale University, New Haven, 06511, CT, USA
| | - Archan Banerjee
- Departments of Applied Physics and Physics, Yale University, New Haven, 06511, CT, USA
- Yale Quantum Institute, Yale University, New Haven, 06511, CT, USA
| | - Chan U Lei
- Departments of Applied Physics and Physics, Yale University, New Haven, 06511, CT, USA
- Yale Quantum Institute, Yale University, New Haven, 06511, CT, USA
| | - Lev Krayzman
- Departments of Applied Physics and Physics, Yale University, New Haven, 06511, CT, USA
- Yale Quantum Institute, Yale University, New Haven, 06511, CT, USA
| | - Kim Kisslinger
- Center for Functional Nanomaterials, Brookhaven National Laboratory, Upton, 11973, NY, USA
| | - Chenyu Zhou
- Center for Functional Nanomaterials, Brookhaven National Laboratory, Upton, 11973, NY, USA
| | - Ruoshui Li
- Center for Functional Nanomaterials, Brookhaven National Laboratory, Upton, 11973, NY, USA
| | - Yichen Jia
- Center for Functional Nanomaterials, Brookhaven National Laboratory, Upton, 11973, NY, USA
| | - Mingzhao Liu
- Center for Functional Nanomaterials, Brookhaven National Laboratory, Upton, 11973, NY, USA
| | - Luigi Frunzio
- Departments of Applied Physics and Physics, Yale University, New Haven, 06511, CT, USA
- Yale Quantum Institute, Yale University, New Haven, 06511, CT, USA
| | - Robert J Schoelkopf
- Departments of Applied Physics and Physics, Yale University, New Haven, 06511, CT, USA.
- Yale Quantum Institute, Yale University, New Haven, 06511, CT, USA.
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2
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Bravyi S, Cross AW, Gambetta JM, Maslov D, Rall P, Yoder TJ. High-threshold and low-overhead fault-tolerant quantum memory. Nature 2024; 627:778-782. [PMID: 38538939 PMCID: PMC10972743 DOI: 10.1038/s41586-024-07107-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2023] [Accepted: 01/23/2024] [Indexed: 04/01/2024]
Abstract
The accumulation of physical errors1-3 prevents the execution of large-scale algorithms in current quantum computers. Quantum error correction4 promises a solution by encoding k logical qubits onto a larger number n of physical qubits, such that the physical errors are suppressed enough to allow running a desired computation with tolerable fidelity. Quantum error correction becomes practically realizable once the physical error rate is below a threshold value that depends on the choice of quantum code, syndrome measurement circuit and decoding algorithm5. We present an end-to-end quantum error correction protocol that implements fault-tolerant memory on the basis of a family of low-density parity-check codes6. Our approach achieves an error threshold of 0.7% for the standard circuit-based noise model, on par with the surface code7-10 that for 20 years was the leading code in terms of error threshold. The syndrome measurement cycle for a length-n code in our family requires n ancillary qubits and a depth-8 circuit with CNOT gates, qubit initializations and measurements. The required qubit connectivity is a degree-6 graph composed of two edge-disjoint planar subgraphs. In particular, we show that 12 logical qubits can be preserved for nearly 1 million syndrome cycles using 288 physical qubits in total, assuming the physical error rate of 0.1%, whereas the surface code would require nearly 3,000 physical qubits to achieve said performance. Our findings bring demonstrations of a low-overhead fault-tolerant quantum memory within the reach of near-term quantum processors.
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Affiliation(s)
- Sergey Bravyi
- IBM Quantum, IBM T.J. Watson Research Center, Yorktown Heights, NY, USA
| | - Andrew W Cross
- IBM Quantum, IBM T.J. Watson Research Center, Yorktown Heights, NY, USA
| | - Jay M Gambetta
- IBM Quantum, IBM T.J. Watson Research Center, Yorktown Heights, NY, USA
| | - Dmitri Maslov
- IBM Quantum, IBM T.J. Watson Research Center, Yorktown Heights, NY, USA.
| | - Patrick Rall
- IBM Quantum, MIT-IBM Watson AI Laboratory, Cambridge, MA, USA
| | - Theodore J Yoder
- IBM Quantum, IBM T.J. Watson Research Center, Yorktown Heights, NY, USA
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3
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Davis EJ, Ye B, Machado F, Meynell SA, Wu W, Mittiga T, Schenken W, Joos M, Kobrin B, Lyu Y, Wang Z, Bluvstein D, Choi S, Zu C, Jayich ACB, Yao NY. Probing many-body dynamics in a two-dimensional dipolar spin ensemble. NATURE PHYSICS 2023; 19:836-844. [PMID: 37323805 PMCID: PMC10264245 DOI: 10.1038/s41567-023-01944-5] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 03/20/2021] [Accepted: 01/05/2023] [Indexed: 06/17/2023]
Abstract
The most direct approach for characterizing the quantum dynamics of a strongly interacting system is to measure the time evolution of its full many-body state. Despite the conceptual simplicity of this approach, it quickly becomes intractable as the system size grows. An alternate approach is to think of the many-body dynamics as generating noise, which can be measured by the decoherence of a probe qubit. Here we investigate what the decoherence dynamics of such a probe tells us about the many-body system. In particular, we utilize optically addressable probe spins to experimentally characterize both static and dynamical properties of strongly interacting magnetic dipoles. Our experimental platform consists of two types of spin defects in nitrogen delta-doped diamond: nitrogen-vacancy colour centres, which we use as probe spins, and a many-body ensemble of substitutional nitrogen impurities. We demonstrate that the many-body system's dimensionality, dynamics and disorder are naturally encoded in the probe spins' decoherence profile. Furthermore, we obtain direct control over the spectral properties of the many-body system, with potential applications in quantum sensing and simulation.
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Affiliation(s)
- E. J. Davis
- Department of Physics, University of California, Berkeley, CA USA
| | - B. Ye
- Department of Physics, University of California, Berkeley, CA USA
| | - F. Machado
- Department of Physics, University of California, Berkeley, CA USA
- Materials Science Division, Lawrence Berkeley National Laboratory, Berkeley, CA USA
| | - S. A. Meynell
- Department of Physics, University of California, Santa Barbara, CA USA
| | - W. Wu
- Department of Physics, University of California, Berkeley, CA USA
- Materials Science Division, Lawrence Berkeley National Laboratory, Berkeley, CA USA
| | - T. Mittiga
- Department of Physics, University of California, Berkeley, CA USA
- Materials Science Division, Lawrence Berkeley National Laboratory, Berkeley, CA USA
| | - W. Schenken
- Department of Physics, University of California, Santa Barbara, CA USA
| | - M. Joos
- Department of Physics, University of California, Santa Barbara, CA USA
| | - B. Kobrin
- Department of Physics, University of California, Berkeley, CA USA
- Materials Science Division, Lawrence Berkeley National Laboratory, Berkeley, CA USA
| | - Y. Lyu
- Department of Physics, University of California, Berkeley, CA USA
| | - Z. Wang
- Department of Physics, University of California, Berkeley, CA USA
- Materials Science Division, Lawrence Berkeley National Laboratory, Berkeley, CA USA
| | - D. Bluvstein
- Department of Physics, Harvard University, Cambridge, MA USA
| | - S. Choi
- Department of Physics, University of California, Berkeley, CA USA
| | - C. Zu
- Department of Physics, University of California, Berkeley, CA USA
- Materials Science Division, Lawrence Berkeley National Laboratory, Berkeley, CA USA
- Department of Physics, Washington University, St. Louis, MO USA
| | | | - N. Y. Yao
- Department of Physics, University of California, Berkeley, CA USA
- Materials Science Division, Lawrence Berkeley National Laboratory, Berkeley, CA USA
- Department of Physics, Harvard University, Cambridge, MA USA
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4
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Zhang X, Kim E, Mark DK, Choi S, Painter O. A superconducting quantum simulator based on a photonic-bandgap metamaterial. Science 2023; 379:278-283. [PMID: 36656924 DOI: 10.1126/science.ade7651] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
Synthesizing many-body quantum systems with various ranges of interactions facilitates the study of quantum chaotic dynamics. Such extended interaction range can be enabled by using nonlocal degrees of freedom such as photonic modes in an otherwise locally connected structure. Here, we present a superconducting quantum simulator in which qubits are connected through an extensible photonic-bandgap metamaterial, thus realizing a one-dimensional Bose-Hubbard model with tunable hopping range and on-site interaction. Using individual site control and readout, we characterize the statistics of measurement outcomes from many-body quench dynamics, which enables in situ Hamiltonian learning. Further, the outcome statistics reveal the effect of increased hopping range, showing the predicted crossover from integrability to ergodicity. Our work enables the study of emergent randomness from chaotic many-body evolution and, more broadly, expands the accessible Hamiltonians for quantum simulation using superconducting circuits.
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Affiliation(s)
- Xueyue Zhang
- Thomas J. Watson, Sr., Laboratory of Applied Physics and Kavli Nanoscience Institute, California Institute of Technology, Pasadena, CA 91125, USA.,Institute for Quantum Information and Matter, California Institute of Technology, Pasadena, CA 91125, USA
| | - Eunjong Kim
- Thomas J. Watson, Sr., Laboratory of Applied Physics and Kavli Nanoscience Institute, California Institute of Technology, Pasadena, CA 91125, USA.,Institute for Quantum Information and Matter, California Institute of Technology, Pasadena, CA 91125, USA
| | - Daniel K Mark
- Center for Theoretical Physics, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - Soonwon Choi
- Center for Theoretical Physics, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - Oskar Painter
- Thomas J. Watson, Sr., Laboratory of Applied Physics and Kavli Nanoscience Institute, California Institute of Technology, Pasadena, CA 91125, USA.,Institute for Quantum Information and Matter, California Institute of Technology, Pasadena, CA 91125, USA.,AWS Center for Quantum Computing, Pasadena, CA 91125, USA
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5
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Circuit quantum electrodynamics with dressed states of a superconducting artificial atom. Sci Rep 2022; 12:22308. [PMID: 36566268 PMCID: PMC9789979 DOI: 10.1038/s41598-022-26828-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2022] [Accepted: 12/20/2022] [Indexed: 12/25/2022] Open
Abstract
A dynamical control of the coupling strengths between dressed states and probe photon states is demonstrated with a transmon-like artificial atom coupled to two closely spaced resonant modes. When the atom is driven with one mode, the atom state and driving photon states form the so-called dressed states. Dressed states with sideband index up to 3 were prepared and probed via the strong coupling to the other resonant mode. Spectroscopy reveals that the coupling strengths are "dressed" and can be modulated by the power and sideband index of the driving. The transmission of the probe tone is modulated by the driving microwave amplitude with a Bessel behavior, displaying multi-photon process associated with the inter-atomic level transitions.
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6
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Fellner M, Messinger A, Ender K, Lechner W. Universal Parity Quantum Computing. PHYSICAL REVIEW LETTERS 2022; 129:180503. [PMID: 36374683 DOI: 10.1103/physrevlett.129.180503] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/19/2022] [Accepted: 09/16/2022] [Indexed: 06/16/2023]
Abstract
We propose a universal gate set for quantum computing with all-to-all connectivity and intrinsic robustness to bit-flip errors based on parity encoding. We show that logical controlled phase gate and R_{z} rotations can be implemented in parity encoding with single-qubit operations. Together with logical R_{x} rotations, implemented via nearest-neighbor controlled-NOT gates and an R_{x} rotation, these form a universal gate set. As the controlled phase gate requires only single-qubit rotations, the proposed scheme has advantages for several cornerstone quantum algorithms, e.g., the quantum Fourier transform. We present a method to switch between different encoding variants via partial on-the-fly encoding and decoding.
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Affiliation(s)
- Michael Fellner
- Institute for Theoretical Physics, University of Innsbruck, A-6020 Innsbruck, Austria
- Parity Quantum Computing GmbH, A-6020 Innsbruck, Austria
| | | | - Kilian Ender
- Institute for Theoretical Physics, University of Innsbruck, A-6020 Innsbruck, Austria
- Parity Quantum Computing GmbH, A-6020 Innsbruck, Austria
| | - Wolfgang Lechner
- Institute for Theoretical Physics, University of Innsbruck, A-6020 Innsbruck, Austria
- Parity Quantum Computing GmbH, A-6020 Innsbruck, Austria
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7
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Delaney RD, Urmey MD, Mittal S, Brubaker BM, Kindem JM, Burns PS, Regal CA, Lehnert KW. Superconducting-qubit readout via low-backaction electro-optic transduction. Nature 2022; 606:489-493. [PMID: 35705821 DOI: 10.1038/s41586-022-04720-2] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2021] [Accepted: 04/04/2022] [Indexed: 11/09/2022]
Abstract
Entangling microwave-frequency superconducting quantum processors through optical light at ambient temperature would enable means of secure communication and distributed quantum information processing1. However, transducing quantum signals between these disparate regimes of the electro-magnetic spectrum remains an outstanding goal2-9, and interfacing superconducting qubits, which are constrained to operate at millikelvin temperatures, with electro-optic transducers presents considerable challenges owing to the deleterious effects of optical photons on superconductors9,10. Moreover, many remote entanglement protocols11-14 require multiple qubit gates both preceding and following the upconversion of the quantum state, and thus an ideal transducer should impart minimal backaction15 on the qubit. Here we demonstrate readout of a superconducting transmon qubit through a low-backaction electro-optomechanical transducer. The modular nature of the transducer and circuit quantum electrodynamics system used in this work enable complete isolation of the qubit from optical photons, and the backaction on the qubit from the transducer is less than that imparted by thermal radiation from the environment. Moderate improvements in the transducer bandwidth and the added noise will enable us to leverage the full suite of tools available in circuit quantum electrodynamics to demonstrate transduction of non-classical signals from a superconducting qubit to the optical domain.
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Affiliation(s)
- R D Delaney
- JILA, National Institute of Standards and Technology and the University of Colorado, Boulder, CO, USA. .,Department of Physics, University of Colorado, Boulder, CO, USA.
| | - M D Urmey
- JILA, National Institute of Standards and Technology and the University of Colorado, Boulder, CO, USA.,Department of Physics, University of Colorado, Boulder, CO, USA
| | - S Mittal
- JILA, National Institute of Standards and Technology and the University of Colorado, Boulder, CO, USA.,Department of Physics, University of Colorado, Boulder, CO, USA
| | - B M Brubaker
- JILA, National Institute of Standards and Technology and the University of Colorado, Boulder, CO, USA.,Department of Physics, University of Colorado, Boulder, CO, USA
| | - J M Kindem
- JILA, National Institute of Standards and Technology and the University of Colorado, Boulder, CO, USA.,Department of Physics, University of Colorado, Boulder, CO, USA
| | - P S Burns
- JILA, National Institute of Standards and Technology and the University of Colorado, Boulder, CO, USA.,Department of Physics, University of Colorado, Boulder, CO, USA
| | - C A Regal
- JILA, National Institute of Standards and Technology and the University of Colorado, Boulder, CO, USA.,Department of Physics, University of Colorado, Boulder, CO, USA
| | - K W Lehnert
- JILA, National Institute of Standards and Technology and the University of Colorado, Boulder, CO, USA.,Department of Physics, University of Colorado, Boulder, CO, USA.,National Institute of Standards and Technology, Boulder, CO, USA
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8
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Spring PA, Cao S, Tsunoda T, Campanaro G, Fasciati S, Wills J, Bakr M, Chidambaram V, Shteynas B, Carpenter L, Gow P, Gates J, Vlastakis B, Leek PJ. High coherence and low cross-talk in a tileable 3D integrated superconducting circuit architecture. SCIENCE ADVANCES 2022; 8:eabl6698. [PMID: 35452292 PMCID: PMC9032975 DOI: 10.1126/sciadv.abl6698] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/26/2021] [Accepted: 03/07/2022] [Indexed: 06/14/2023]
Abstract
We report high qubit coherence as well as low cross-talk and single-qubit gate errors in a superconducting circuit architecture that promises to be tileable to two-dimensional (2D) lattices of qubits. The architecture integrates an inductively shunted cavity enclosure into a design featuring nongalvanic out-of-plane control wiring and qubits and resonators fabricated on opposing sides of a substrate. The proof-of-principle device features four uncoupled transmon qubits and exhibits average energy relaxation times T1 = 149(38) μs, pure echoed dephasing times Tϕ,e = 189(34) μs, and single-qubit gate fidelities F = 99.982(4)% as measured by simultaneous randomized benchmarking. The 3D integrated nature of the control wiring means that qubits will remain addressable as the architecture is tiled to form larger qubit lattices. Band structure simulations are used to predict that the tiled enclosure will still provide a clean electromagnetic environment to enclosed qubits at arbitrary scale.
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Affiliation(s)
- Peter A. Spring
- Clarendon Laboratory, Department of Physics, University of Oxford, Oxford OX1 3PU, UK
| | - Shuxiang Cao
- Clarendon Laboratory, Department of Physics, University of Oxford, Oxford OX1 3PU, UK
| | - Takahiro Tsunoda
- Clarendon Laboratory, Department of Physics, University of Oxford, Oxford OX1 3PU, UK
| | - Giulio Campanaro
- Clarendon Laboratory, Department of Physics, University of Oxford, Oxford OX1 3PU, UK
| | - Simone Fasciati
- Clarendon Laboratory, Department of Physics, University of Oxford, Oxford OX1 3PU, UK
| | - James Wills
- Clarendon Laboratory, Department of Physics, University of Oxford, Oxford OX1 3PU, UK
| | - Mustafa Bakr
- Clarendon Laboratory, Department of Physics, University of Oxford, Oxford OX1 3PU, UK
| | - Vivek Chidambaram
- Clarendon Laboratory, Department of Physics, University of Oxford, Oxford OX1 3PU, UK
| | - Boris Shteynas
- Clarendon Laboratory, Department of Physics, University of Oxford, Oxford OX1 3PU, UK
| | - Lewis Carpenter
- Optoelectronics Research Centre, University of Southampton, Southampton SO17 1BJ, UK
| | - Paul Gow
- Optoelectronics Research Centre, University of Southampton, Southampton SO17 1BJ, UK
| | - James Gates
- Optoelectronics Research Centre, University of Southampton, Southampton SO17 1BJ, UK
| | - Brian Vlastakis
- Clarendon Laboratory, Department of Physics, University of Oxford, Oxford OX1 3PU, UK
| | - Peter J. Leek
- Clarendon Laboratory, Department of Physics, University of Oxford, Oxford OX1 3PU, UK
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9
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Control and readout of a superconducting qubit using a photonic link. Nature 2021; 591:575-579. [PMID: 33762768 DOI: 10.1038/s41586-021-03268-x] [Citation(s) in RCA: 30] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2020] [Accepted: 01/20/2021] [Indexed: 02/01/2023]
Abstract
Delivering on the revolutionary promise of a universal quantum computer will require processors with millions of quantum bits (qubits)1-3. In superconducting quantum processors4, each qubit is individually addressed with microwave signal lines that connect room-temperature electronics to the cryogenic environment of the quantum circuit. The complexity and heat load associated with the multiple coaxial lines per qubit limits the maximum possible size of a processor to a few thousand qubits5. Here we introduce a photonic link using an optical fibre to guide modulated laser light from room temperature to a cryogenic photodetector6, capable of delivering shot-noise-limited microwave signals directly at millikelvin temperatures. By demonstrating high-fidelity control and readout of a superconducting qubit, we show that this photonic link can meet the stringent requirements of superconducting quantum information processing7. Leveraging the low thermal conductivity and large intrinsic bandwidth of optical fibre enables the efficient and massively multiplexed delivery of coherent microwave control pulses, providing a path towards a million-qubit universal quantum computer.
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10
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Chiu KL, Qian D, Qiu J, Liu W, Tan D, Mosallanejad V, Liu S, Zhang Z, Zhao Y, Yu D. Flux Tunable Superconducting Quantum Circuit Based on Weyl Semimetal MoTe 2. NANO LETTERS 2020; 20:8469-8475. [PMID: 33174417 DOI: 10.1021/acs.nanolett.0c02267] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Weyl semimetals have drawn considerable attention for their exotic topological properties in many research fields. When in combination with s-wave superconductors, the supercurrent can be carried by their topological surface channels, forming junctions mimicking the behavior of Majorana bound states. Here, we present a transmon-like superconducting quantum intereference device (SQUID) consisting of lateral junctions made of Weyl semimetal Td-MoTe2 and superconducting leads of niobium nitride (NbN). The SQUID is coupled to a readout cavity made of molybdenum rhenium (MoRe), whose response at high power reveals the existence of the constituting Josephson junctions (JJs). The loop geometry of the circuit allows the resonant frequency of the readout cavity to be tuned by the magnetic flux. We demonstrate a JJ made of MoTe2 and a flux-tunable transmon-like circuit based on Weyl semimetals. Our study provides a platform to utilize topological materials in SQUID-based quantum circuits for potential applications in quantum information processing.
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Affiliation(s)
- Kuei-Lin Chiu
- Department of Physics, National Sun Yat-Sen University, Kaohsiung 80424, Taiwan
| | - Degui Qian
- Shenzhen Institute for Quantum Science and Engineering, Southern University of Science and Technology, Shenzhen 518055, China
| | - Jiawei Qiu
- Shenzhen Institute for Quantum Science and Engineering, Southern University of Science and Technology, Shenzhen 518055, China
| | - Weiyang Liu
- Shenzhen Institute for Quantum Science and Engineering, Southern University of Science and Technology, Shenzhen 518055, China
| | - Dian Tan
- Shenzhen Institute for Quantum Science and Engineering, Southern University of Science and Technology, Shenzhen 518055, China
| | - Vahid Mosallanejad
- Key Lab of Quantum Information, University of Science and Technology of China, Hefei 230026, China
| | - Song Liu
- Shenzhen Institute for Quantum Science and Engineering, Southern University of Science and Technology, Shenzhen 518055, China
| | - Zongteng Zhang
- Shenzhen Institute for Quantum Science and Engineering, Southern University of Science and Technology, Shenzhen 518055, China
| | - Yue Zhao
- Shenzhen Institute for Quantum Science and Engineering, Southern University of Science and Technology, Shenzhen 518055, China
| | - Dapeng Yu
- Shenzhen Institute for Quantum Science and Engineering, Southern University of Science and Technology, Shenzhen 518055, China
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11
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McRae CRH, Wang H, Gao J, Vissers MR, Brecht T, Dunsworth A, Pappas DP, Mutus J. Materials loss measurements using superconducting microwave resonators. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2020; 91:091101. [PMID: 33003823 DOI: 10.1063/5.0017378] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/07/2020] [Accepted: 08/20/2020] [Indexed: 06/11/2023]
Abstract
The performance of superconducting circuits for quantum computing is limited by materials losses. In particular, coherence times are typically bounded by two-level system (TLS) losses at single photon powers and millikelvin temperatures. The identification of low loss fabrication techniques, materials, and thin film dielectrics is critical to achieving scalable architectures for superconducting quantum computing. Superconducting microwave resonators provide a convenient qubit proxy for assessing performance and studying TLS loss and other mechanisms relevant to superconducting circuits such as non-equilibrium quasiparticles and magnetic flux vortices. In this review article, we provide an overview of considerations for designing accurate resonator experiments to characterize loss, including applicable types of losses, cryogenic setup, device design, and methods for extracting material and interface losses, summarizing techniques that have been evolving for over two decades. Results from measurements of a wide variety of materials and processes are also summarized. Finally, we present recommendations for the reporting of loss data from superconducting microwave resonators to facilitate materials comparisons across the field.
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Affiliation(s)
- C R H McRae
- Department of Physics, University of Colorado, Boulder, Colorado 80309, USA
| | - H Wang
- Department of Physics, University of Colorado, Boulder, Colorado 80309, USA
| | - J Gao
- Department of Physics, University of Colorado, Boulder, Colorado 80309, USA
| | - M R Vissers
- National Institute of Standards and Technology, Boulder, Colorado 80305, USA
| | - T Brecht
- HRL Laboratories, Malibu, California 90265, USA
| | - A Dunsworth
- Google, Inc., Mountain View, California 94043, USA
| | - D P Pappas
- National Institute of Standards and Technology, Boulder, Colorado 80305, USA
| | - J Mutus
- Boulder Cryogenic Quantum Testbed, University of Colorado, Boulder, Colorado 80309, USA
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12
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Kono S, Koshino K, Lachance-Quirion D, van Loo AF, Tabuchi Y, Noguchi A, Nakamura Y. Breaking the trade-off between fast control and long lifetime of a superconducting qubit. Nat Commun 2020; 11:3683. [PMID: 32703942 PMCID: PMC7378077 DOI: 10.1038/s41467-020-17511-y] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2020] [Accepted: 07/05/2020] [Indexed: 11/23/2022] Open
Abstract
The rapid development in designs and fabrication techniques of superconducting qubits has made coherence times of qubits longer. In the future, however, the radiative decay of a qubit into its control line will be a fundamental limitation, imposing a trade-off between fast control and long lifetime of the qubit. Here, we break this trade-off by strongly coupling another superconducting qubit along the control line. This second qubit, which we call “Josephson quantum filter” (JQF), prevents the first qubit from emitting microwave photons and thus suppresses its relaxation, while transmitting large-amplitude control microwave pulses due to the saturation of the quantum filter, enabling fast qubit control. This device functions as an automatic decoupler between a qubit and its control line and could help in the realization of a large-scale superconducting quantum processor by reducing the heating of the qubit environment and the crosstalk between qubits. The trade-off between long lifetime and inevitable radiative decay to a control line has become a key limitation for superconducting qubits. Here, the authors break the trade-off by coupling another qubit to the control line of the first one to suppress its relaxation, while enabling fast qubit control.
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Affiliation(s)
- S Kono
- Center for Emergent Matter Science (CEMS), RIKEN, Wako, Saitama, 351-0198, Japan.
| | - K Koshino
- College of Liberal Arts and Sciences, Tokyo Medical and Dental University, Ichikawa, Chiba, 272-0827, Japan
| | - D Lachance-Quirion
- Research Center for Advanced Science and Technology (RCAST), The University of Tokyo, Meguro-ku, Tokyo, 153-8904, Japan.,Institut Quantique and Département de Physique, Université de Sherbrooke, Sherbrooke, QC, J1K 2R1, Canada
| | - A F van Loo
- Center for Emergent Matter Science (CEMS), RIKEN, Wako, Saitama, 351-0198, Japan
| | - Y Tabuchi
- Research Center for Advanced Science and Technology (RCAST), The University of Tokyo, Meguro-ku, Tokyo, 153-8904, Japan
| | - A Noguchi
- Komaba Institute for Science (KIS), The University of Tokyo, Meguro-ku, Tokyo, 153-8902, Japan.,PRESTO, Japan Science and Technology Agency, Kawaguchi-shi, Saitama, 332-0012, Japan
| | - Y Nakamura
- Center for Emergent Matter Science (CEMS), RIKEN, Wako, Saitama, 351-0198, Japan. .,Research Center for Advanced Science and Technology (RCAST), The University of Tokyo, Meguro-ku, Tokyo, 153-8904, Japan.
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13
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Kringhøj A, Larsen TW, van Heck B, Sabonis D, Erlandsson O, Petkovic I, Pikulin DI, Krogstrup P, Petersson KD, Marcus CM. Controlled dc Monitoring of a Superconducting Qubit. PHYSICAL REVIEW LETTERS 2020; 124:056801. [PMID: 32083909 DOI: 10.1103/physrevlett.124.056801] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/17/2019] [Accepted: 12/23/2019] [Indexed: 06/10/2023]
Abstract
Creating a transmon qubit using semiconductor-superconductor hybrid materials not only provides electrostatic control of the qubit frequency, it also allows parts of the circuit to be electrically connected and disconnected in situ by operating a semiconductor region of the device as a field-effect transistor. Here, we exploit this feature to compare in the same device characteristics of the qubit, such as frequency and relaxation time, with related transport properties such as critical supercurrent and normal-state resistance. Gradually opening the field-effect transistor to the monitoring circuit allows the influence of weak-to-strong dc monitoring of a "live" qubit to be measured. A model of this influence yields excellent agreement with experiment, demonstrating a relaxation rate mediated by a gate-controlled environmental coupling.
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Affiliation(s)
- A Kringhøj
- Microsoft Quantum Lab Copenhagen and Center for Quantum Devices, Niels Bohr Institute, University of Copenhagen, Universitetsparken 5, 2100 Copenhagen, Denmark
| | - T W Larsen
- Microsoft Quantum Lab Copenhagen and Center for Quantum Devices, Niels Bohr Institute, University of Copenhagen, Universitetsparken 5, 2100 Copenhagen, Denmark
| | - B van Heck
- Microsoft Quantum, Station Q, University of California, Santa Barbara, California 93106-6105, USA
- Microsoft Quantum Lab Delft, Delft University of Technology, 2600 GA Delft, Netherlands
| | - D Sabonis
- Microsoft Quantum Lab Copenhagen and Center for Quantum Devices, Niels Bohr Institute, University of Copenhagen, Universitetsparken 5, 2100 Copenhagen, Denmark
| | - O Erlandsson
- Microsoft Quantum Lab Copenhagen and Center for Quantum Devices, Niels Bohr Institute, University of Copenhagen, Universitetsparken 5, 2100 Copenhagen, Denmark
| | - I Petkovic
- Microsoft Quantum Lab Copenhagen and Center for Quantum Devices, Niels Bohr Institute, University of Copenhagen, Universitetsparken 5, 2100 Copenhagen, Denmark
| | - D I Pikulin
- Microsoft Quantum, Station Q, University of California, Santa Barbara, California 93106-6105, USA
| | - P Krogstrup
- Microsoft Quantum Lab Copenhagen and Center for Quantum Devices, Niels Bohr Institute, University of Copenhagen, Universitetsparken 5, 2100 Copenhagen, Denmark
- Microsoft Quantum Materials Lab Copenhagen, Kanalvej 7, 2800 Lyngby, Denmark
| | - K D Petersson
- Microsoft Quantum Lab Copenhagen and Center for Quantum Devices, Niels Bohr Institute, University of Copenhagen, Universitetsparken 5, 2100 Copenhagen, Denmark
| | - C M Marcus
- Microsoft Quantum Lab Copenhagen and Center for Quantum Devices, Niels Bohr Institute, University of Copenhagen, Universitetsparken 5, 2100 Copenhagen, Denmark
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14
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Abstract
Spin qubits and superconducting qubits are among the promising candidates for realizing a solid state quantum computer. For the implementation of a hybrid architecture which can profit from the advantages of either approach, a coherent link is necessary that integrates and controllably couples both qubit types on the same chip over a distance that is several orders of magnitude longer than the physical size of the spin qubit. We realize such a link with a frequency-tunable high impedance SQUID array resonator. The spin qubit is a resonant exchange qubit hosted in a GaAs triple quantum dot. It can be operated at zero magnetic field, allowing it to coexist with superconducting qubits on the same chip. We spectroscopically observe coherent interaction between the resonant exchange qubit and a transmon qubit in both resonant and dispersive regimes, where the interaction is mediated either by real or virtual resonator photons. Different qubit platforms each have their own advantages and disadvantages. By engineering couplings between them it may be possible to create a more capable hybrid device. Here the authors demonstrate coherent coupling between a semiconductor spin qubit and a superconducting transmon.
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15
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Huang Z, Zheng F, Zhang Y, Wei Y, Zhao Y. Dissipative dynamics in a tunable Rabi dimer with periodic harmonic driving. J Chem Phys 2019; 150:184116. [PMID: 31091928 DOI: 10.1063/1.5096071] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Recent progress on qubit manipulation allows application of periodic driving signals on qubits. In this study, a harmonic driving field is added to a Rabi dimer to engineer photon and qubit dynamics in a circuit quantum electrodynamics device. To model environmental effects, qubits in the Rabi dimer are coupled to a phonon bath with a sub-Ohmic spectral density. A nonperturbative treatment, the Dirac-Frenkel time-dependent variational principle together with the multiple Davydov D2 ansatz, is employed to explore the dynamical behavior of the tunable Rabi dimer. In the absence of the phonon bath, the amplitude damping of the photon number oscillation is greatly suppressed by the driving field, and photons can be created, thanks to the resonance between the periodic driving field and the photon frequency. In the presence of the phonon bath, one can still change the photon numbers in two resonators and indirectly alter the photon imbalance in the Rabi dimer by directly varying the driving signal in one qubit. It is shown that qubit states can be manipulated directly by the harmonic driving. The environment is found to strengthen the interqubit asymmetry induced by the external driving, opening up a new venue to engineer the qubit states.
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Affiliation(s)
- Zhongkai Huang
- Division of Materials Science, Nanyang Technological University, Singapore 639798, Singapore
| | - Fulu Zheng
- Division of Materials Science, Nanyang Technological University, Singapore 639798, Singapore
| | - Yuyu Zhang
- Department of Physics, Chongqing University, Chongqing 404100, China
| | - Yadong Wei
- School of Physics and Energy, Shenzhen University, Shenzhen 518060, China
| | - Yang Zhao
- Division of Materials Science, Nanyang Technological University, Singapore 639798, Singapore
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16
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Touzard S, Kou A, Frattini NE, Sivak VV, Puri S, Grimm A, Frunzio L, Shankar S, Devoret MH. Gated Conditional Displacement Readout of Superconducting Qubits. PHYSICAL REVIEW LETTERS 2019; 122:080502. [PMID: 30932609 DOI: 10.1103/physrevlett.122.080502] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/19/2018] [Indexed: 06/09/2023]
Abstract
We have realized a new interaction between superconducting qubits and a readout cavity that results in the displacement of a coherent state in the cavity, conditioned on the state of the qubit. This conditional state, when it reaches the cavity-following, phase-sensitive amplifier, matches its measured observable, namely, the in phase quadrature. In a setup where several qubits are coupled to the same readout resonator, we show it is possible to measure the state of a target qubit with minimal dephasing of the other qubits. Our results suggest novel directions for faster readout of superconducting qubits and implementations of bosonic quantum error-correcting codes.
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Affiliation(s)
- S Touzard
- Department of Applied Physics and Physics, Yale University, New Haven, Connecticut 06520, USA
| | - A Kou
- Department of Applied Physics and Physics, Yale University, New Haven, Connecticut 06520, USA
| | - N E Frattini
- Department of Applied Physics and Physics, Yale University, New Haven, Connecticut 06520, USA
| | - V V Sivak
- Department of Applied Physics and Physics, Yale University, New Haven, Connecticut 06520, USA
| | - S Puri
- Yale Quantum Institute, Yale University, New Haven, Connecticut 06520, USA
| | - A Grimm
- Department of Applied Physics and Physics, Yale University, New Haven, Connecticut 06520, USA
| | - L Frunzio
- Department of Applied Physics and Physics, Yale University, New Haven, Connecticut 06520, USA
| | - S Shankar
- Department of Applied Physics and Physics, Yale University, New Haven, Connecticut 06520, USA
| | - M H Devoret
- Department of Applied Physics and Physics, Yale University, New Haven, Connecticut 06520, USA
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17
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Hazard TM, Gyenis A, Di Paolo A, Asfaw AT, Lyon SA, Blais A, Houck AA. Nanowire Superinductance Fluxonium Qubit. PHYSICAL REVIEW LETTERS 2019; 122:010504. [PMID: 31012689 DOI: 10.1103/physrevlett.122.010504] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/30/2018] [Revised: 10/05/2018] [Indexed: 06/09/2023]
Abstract
We characterize a fluxonium qubit consisting of a Josephson junction inductively shunted with a NbTiN nanowire superinductance. We explain the measured energy spectrum by means of a multimode theory accounting for the distributed nature of the superinductance and the effect of the circuit nonlinearity to all orders in the Josephson potential. Using multiphoton Raman spectroscopy, we address multiple fluxonium transitions, observe multilevel Autler-Townes splitting and measure an excited state lifetime of T_{1}=20 μs. By measuring T_{1} at different magnetic flux values, we find a crossover in the lifetime limiting mechanism from capacitive to inductive losses.
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Affiliation(s)
- T M Hazard
- Department of Electrical Engineering, Princeton University, Princeton, New Jersey 08544, USA
| | - A Gyenis
- Department of Electrical Engineering, Princeton University, Princeton, New Jersey 08544, USA
| | - A Di Paolo
- Department of Electrical Engineering, Princeton University, Princeton, New Jersey 08544, USA
| | - A T Asfaw
- Department of Electrical Engineering, Princeton University, Princeton, New Jersey 08544, USA
| | - S A Lyon
- Department of Electrical Engineering, Princeton University, Princeton, New Jersey 08544, USA
| | - A Blais
- Institut quantique and Département de Physique, Université de Sherbrooke, Sherbrooke J1K 2R1 Quebec, Canada
- Canadian Institute for Advanced Research, Toronto, M5G 1M1 Ontario, Canada
| | - A A Houck
- Department of Electrical Engineering, Princeton University, Princeton, New Jersey 08544, USA
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18
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Klimov PV, Kelly J, Chen Z, Neeley M, Megrant A, Burkett B, Barends R, Arya K, Chiaro B, Chen Y, Dunsworth A, Fowler A, Foxen B, Gidney C, Giustina M, Graff R, Huang T, Jeffrey E, Lucero E, Mutus JY, Naaman O, Neill C, Quintana C, Roushan P, Sank D, Vainsencher A, Wenner J, White TC, Boixo S, Babbush R, Smelyanskiy VN, Neven H, Martinis JM. Fluctuations of Energy-Relaxation Times in Superconducting Qubits. PHYSICAL REVIEW LETTERS 2018; 121:090502. [PMID: 30230854 DOI: 10.1103/physrevlett.121.090502] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/18/2018] [Indexed: 06/08/2023]
Abstract
Superconducting qubits are an attractive platform for quantum computing since they have demonstrated high-fidelity quantum gates and extensibility to modest system sizes. Nonetheless, an outstanding challenge is stabilizing their energy-relaxation times, which can fluctuate unpredictably in frequency and time. Here, we use qubits as spectral and temporal probes of individual two-level-system defects to provide direct evidence that they are responsible for the largest fluctuations. This research lays the foundation for stabilizing qubit performance through calibration, design, and fabrication.
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Affiliation(s)
- P V Klimov
- Google, Santa Barbara, California 93117, USA
| | - J Kelly
- Google, Santa Barbara, California 93117, USA
| | - Z Chen
- Google, Santa Barbara, California 93117, USA
| | - M Neeley
- Google, Santa Barbara, California 93117, USA
| | - A Megrant
- Google, Santa Barbara, California 93117, USA
| | - B Burkett
- Google, Santa Barbara, California 93117, USA
| | - R Barends
- Google, Santa Barbara, California 93117, USA
| | - K Arya
- Google, Santa Barbara, California 93117, USA
| | - B Chiaro
- University of California, Santa Barbara, California 93106, USA
| | - Yu Chen
- Google, Santa Barbara, California 93117, USA
| | - A Dunsworth
- University of California, Santa Barbara, California 93106, USA
| | - A Fowler
- Google, Santa Barbara, California 93117, USA
| | - B Foxen
- University of California, Santa Barbara, California 93106, USA
| | - C Gidney
- Google, Santa Barbara, California 93117, USA
| | - M Giustina
- Google, Santa Barbara, California 93117, USA
| | - R Graff
- Google, Santa Barbara, California 93117, USA
| | - T Huang
- Google, Santa Barbara, California 93117, USA
| | - E Jeffrey
- Google, Santa Barbara, California 93117, USA
| | - Erik Lucero
- Google, Santa Barbara, California 93117, USA
| | - J Y Mutus
- Google, Santa Barbara, California 93117, USA
| | - O Naaman
- Google, Santa Barbara, California 93117, USA
| | - C Neill
- Google, Santa Barbara, California 93117, USA
| | - C Quintana
- Google, Santa Barbara, California 93117, USA
| | - P Roushan
- Google, Santa Barbara, California 93117, USA
| | - Daniel Sank
- Google, Santa Barbara, California 93117, USA
| | | | - J Wenner
- University of California, Santa Barbara, California 93106, USA
| | - T C White
- Google, Santa Barbara, California 93117, USA
| | - S Boixo
- Google, Los Angeles, California 90291, USA
| | - R Babbush
- Google, Los Angeles, California 90291, USA
| | | | - H Neven
- Google, Los Angeles, California 90291, USA
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19
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Yan F, Campbell D, Krantz P, Kjaergaard M, Kim D, Yoder JL, Hover D, Sears A, Kerman AJ, Orlando TP, Gustavsson S, Oliver WD. Distinguishing Coherent and Thermal Photon Noise in a Circuit Quantum Electrodynamical System. PHYSICAL REVIEW LETTERS 2018; 120:260504. [PMID: 30004727 DOI: 10.1103/physrevlett.120.260504] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/01/2018] [Indexed: 06/08/2023]
Abstract
In the cavity-QED architecture, photon number fluctuations from residual cavity photons cause qubit dephasing due to the ac Stark effect. These unwanted photons originate from a variety of sources, such as thermal radiation, leftover measurement photons, and cross talk. Using a capacitively shunted flux qubit coupled to a transmission line cavity, we demonstrate a method that identifies and distinguishes coherent and thermal photons based on noise-spectral reconstruction from time-domain spin-locking relaxometry. Using these measurements, we attribute the limiting dephasing source in our system to thermal photons rather than coherent photons. By improving the cryogenic attenuation on lines leading to the cavity, we successfully suppress residual thermal photons and achieve T_{1}-limited spin-echo decay time. The spin-locking noise-spectroscopy technique allows broad frequency access and readily applies to other qubit modalities for identifying general asymmetric nonclassical noise spectra.
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Affiliation(s)
- Fei Yan
- Research Laboratory of Electronics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
| | - Dan Campbell
- Research Laboratory of Electronics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
| | - Philip Krantz
- Research Laboratory of Electronics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
| | - Morten Kjaergaard
- Research Laboratory of Electronics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
| | - David Kim
- MIT Lincoln Laboratory, 244 Wood Street, Lexington, Massachusetts 02420, USA
| | - Jonilyn L Yoder
- MIT Lincoln Laboratory, 244 Wood Street, Lexington, Massachusetts 02420, USA
| | - David Hover
- MIT Lincoln Laboratory, 244 Wood Street, Lexington, Massachusetts 02420, USA
| | - Adam Sears
- MIT Lincoln Laboratory, 244 Wood Street, Lexington, Massachusetts 02420, USA
| | - Andrew J Kerman
- MIT Lincoln Laboratory, 244 Wood Street, Lexington, Massachusetts 02420, USA
| | - Terry P Orlando
- Research Laboratory of Electronics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
| | - Simon Gustavsson
- Research Laboratory of Electronics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
| | - William D Oliver
- Research Laboratory of Electronics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
- MIT Lincoln Laboratory, 244 Wood Street, Lexington, Massachusetts 02420, USA
- Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
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20
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Resolution of superluminal signalling in non-perturbative cavity quantum electrodynamics. Nat Commun 2018; 9:1924. [PMID: 29765054 PMCID: PMC5954151 DOI: 10.1038/s41467-018-04339-w] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2017] [Accepted: 04/23/2018] [Indexed: 12/04/2022] Open
Abstract
Recent technological developments have made it increasingly easy to access the non-perturbative regimes of cavity quantum electrodynamics known as ultrastrong or deep strong coupling, where the light–matter coupling becomes comparable to the bare modal frequencies. In this work, we address the adequacy of the broadly used single-mode cavity approximation to describe such regimes. We demonstrate that, in the non-perturbative light–matter coupling regimes, the single-mode models become unphysical, allowing for superluminal signalling. Moreover, considering the specific example of the quantum Rabi model, we show that the multi-mode description of the electromagnetic field, necessary to account for light propagation at finite speed, yields physical observables that differ radically from their single-mode counterparts already for moderate values of the coupling. Our multi-mode analysis also reveals phenomena of fundamental interest on the dynamics of the intracavity electric field, where a free photonic wavefront and a bound state of virtual photons are shown to coexist. Quantum Rabi model is a standard tool for describing cavity quantum electrodynamics, but the potential shortcomings of its single-mode version are usually neglected. Here, the authors show that, in the ultrastrong coupling regime, a multimode Rabi model is mandatory in order to avoid unphysical results.
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21
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Earnest N, Chakram S, Lu Y, Irons N, Naik RK, Leung N, Ocola L, Czaplewski DA, Baker B, Lawrence J, Koch J, Schuster DI. Realization of a Λ System with Metastable States of a Capacitively Shunted Fluxonium. PHYSICAL REVIEW LETTERS 2018; 120:150504. [PMID: 29756860 DOI: 10.1103/physrevlett.120.150504] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/12/2017] [Indexed: 06/08/2023]
Abstract
We realize a Λ system in a superconducting circuit, with metastable states exhibiting lifetimes up to 8 ms. We exponentially suppress the tunneling matrix elements involved in spontaneous energy relaxation by creating a "heavy" fluxonium, realized by adding a capacitive shunt to the original circuit design. The device allows for both cavity-assisted and direct fluorescent readouts, as well as state preparation schemes akin to optical pumping. Since direct transitions between the metastable states are strongly suppressed, we utilize Raman transitions for coherent manipulation of the states.
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Affiliation(s)
- N Earnest
- The James Franck Institute and Department of Physics, University of Chicago, Chicago, Illinois 60637, USA
| | - S Chakram
- The James Franck Institute and Department of Physics, University of Chicago, Chicago, Illinois 60637, USA
| | - Y Lu
- The James Franck Institute and Department of Physics, University of Chicago, Chicago, Illinois 60637, USA
| | - N Irons
- Department of Physics and Astronomy, Northwestern University, Evanston, Illinois 60208, USA
| | - R K Naik
- The James Franck Institute and Department of Physics, University of Chicago, Chicago, Illinois 60637, USA
| | - N Leung
- The James Franck Institute and Department of Physics, University of Chicago, Chicago, Illinois 60637, USA
| | - L Ocola
- Argonne National Laboratories, Center for Nanoscale Materials, Argonne, Illinois 60439, USA
| | - D A Czaplewski
- Argonne National Laboratories, Center for Nanoscale Materials, Argonne, Illinois 60439, USA
| | - B Baker
- Department of Physics and Astronomy, Northwestern University, Evanston, Illinois 60208, USA
| | - Jay Lawrence
- Department of Physics, Dartmouth College, Hanover, New Hampshire 03755, USA
| | - Jens Koch
- Department of Physics and Astronomy, Northwestern University, Evanston, Illinois 60208, USA
| | - D I Schuster
- The James Franck Institute and Department of Physics, University of Chicago, Chicago, Illinois 60637, USA
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22
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Ding JH, Huai SN, Ian H, Liu YX. Vacuum induced transparency and photon number resolved Autler-Townes splitting in a three-level system. Sci Rep 2018. [PMID: 29540786 PMCID: PMC5852031 DOI: 10.1038/s41598-018-22666-2] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
Abstract
We study the absorption spectrum of a probe field by a Λ-type three-level system, which is coupled to a quantized control field through the two upper energy levels. The probe field is applied to the ground and the second excited states. When the quantized control field is in vacuum, we derive a threshold condition to discern vacuum induced transparency (VIT) and vacuum induced Autler-Townes splitting (ATS). We also find that the parameter changing from VIT to vacuum induced ATS is very similar to that from broken PT symmetry to PT symmetry. Moreover, we find the photon number resolved spectrum in the parameter regime of vacuum induced ATS when the mean photon number of the quantized control field is changed from zero (vacuum) to a finite number. However, there is no photon number resolved spectrum in the parameter regime of VIT even that the quantized control field contains the finite number of photons. Finally, we further discuss possible experimental realization.
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Affiliation(s)
- Jiang-Hao Ding
- Institute of Microelectronics, Tsinghua University, Beijing, 100084, China.,Institute of Applied Physics and Materials Engineering, University of Macau, 999078, Macau, China
| | - Sai-Nan Huai
- Institute of Microelectronics, Tsinghua University, Beijing, 100084, China
| | - Hou Ian
- Institute of Applied Physics and Materials Engineering, University of Macau, 999078, Macau, China
| | - Yu-Xi Liu
- Institute of Microelectronics, Tsinghua University, Beijing, 100084, China. .,Tsinghua National Laboratory for Information Science and Technology (TNList), Beijing, 100084, China.
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23
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Luthi F, Stavenga T, Enzing OW, Bruno A, Dickel C, Langford NK, Rol MA, Jespersen TS, Nygård J, Krogstrup P, DiCarlo L. Evolution of Nanowire Transmon Qubits and Their Coherence in a Magnetic Field. PHYSICAL REVIEW LETTERS 2018; 120:100502. [PMID: 29570312 DOI: 10.1103/physrevlett.120.100502] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/22/2017] [Indexed: 06/08/2023]
Abstract
We present an experimental study of flux- and gate-tunable nanowire transmons with state-of-the-art relaxation time allowing quantitative extraction of flux and charge noise coupling to the Josephson energy. We evidence coherence sweet spots for charge, tuned by voltage on a proximal side gate, where first order sensitivity to switching two-level systems and background 1/f noise is minimized. Next, we investigate the evolution of a nanowire transmon in a parallel magnetic field up to 70 mT, the upper bound set by the closing of the induced gap. Several features observed in the field dependence of qubit energy relaxation and dephasing times are not fully understood. Using nanowires with a thinner, partially covering Al shell will enable operation of these circuits up to 0.5 T, a regime relevant for topological quantum computation and other applications.
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Affiliation(s)
- F Luthi
- QuTech, Delft University of Technology, Lorentzweg 1, 2628 CJ Delft, Netherlands
- Kavli Institute of Nanoscience, Delft University of Technology, Lorentzweg 1, 2628 CJ Delft, Netherlands
| | - T Stavenga
- QuTech, Delft University of Technology, Lorentzweg 1, 2628 CJ Delft, Netherlands
- Kavli Institute of Nanoscience, Delft University of Technology, Lorentzweg 1, 2628 CJ Delft, Netherlands
| | - O W Enzing
- QuTech, Delft University of Technology, Lorentzweg 1, 2628 CJ Delft, Netherlands
- Kavli Institute of Nanoscience, Delft University of Technology, Lorentzweg 1, 2628 CJ Delft, Netherlands
| | - A Bruno
- QuTech, Delft University of Technology, Lorentzweg 1, 2628 CJ Delft, Netherlands
- Kavli Institute of Nanoscience, Delft University of Technology, Lorentzweg 1, 2628 CJ Delft, Netherlands
| | - C Dickel
- QuTech, Delft University of Technology, Lorentzweg 1, 2628 CJ Delft, Netherlands
- Kavli Institute of Nanoscience, Delft University of Technology, Lorentzweg 1, 2628 CJ Delft, Netherlands
| | - N K Langford
- QuTech, Delft University of Technology, Lorentzweg 1, 2628 CJ Delft, Netherlands
- Kavli Institute of Nanoscience, Delft University of Technology, Lorentzweg 1, 2628 CJ Delft, Netherlands
| | - M A Rol
- QuTech, Delft University of Technology, Lorentzweg 1, 2628 CJ Delft, Netherlands
- Kavli Institute of Nanoscience, Delft University of Technology, Lorentzweg 1, 2628 CJ Delft, Netherlands
| | - T S Jespersen
- Center for Quantum Devices, Niels Bohr Institute, University of Copenhagen, DK-2100 Copenhagen, Denmark
| | - J Nygård
- Center for Quantum Devices, Niels Bohr Institute, University of Copenhagen, DK-2100 Copenhagen, Denmark
- Nano-Science Center, Niels Bohr Institute, University of Copenhagen, DK-2100 Copenhagen, Denmark
| | - P Krogstrup
- Center for Quantum Devices, Niels Bohr Institute, University of Copenhagen, DK-2100 Copenhagen, Denmark
| | - L DiCarlo
- QuTech, Delft University of Technology, Lorentzweg 1, 2628 CJ Delft, Netherlands
- Kavli Institute of Nanoscience, Delft University of Technology, Lorentzweg 1, 2628 CJ Delft, Netherlands
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24
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Malekakhlagh M, Petrescu A, Türeci HE. Cutoff-Free Circuit Quantum Electrodynamics. PHYSICAL REVIEW LETTERS 2017; 119:073601. [PMID: 28949687 DOI: 10.1103/physrevlett.119.073601] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/20/2017] [Indexed: 06/07/2023]
Abstract
Any quantum-confined electronic system coupled to the electromagnetic continuum is subject to radiative decay and renormalization of its energy levels. When coupled to a cavity, these quantities can be strongly modified with respect to their values in vacuum. Generally, this modification can be accurately captured by including only the closest resonant mode of the cavity. In the circuit quantum electrodynamics architecture, it is, however, found that the radiative decay rates are strongly influenced by far off-resonant modes. A multimode calculation accounting for the infinite set of cavity modes leads to divergences unless a cutoff is imposed. It has so far not been identified what the source of divergence is. We show here that unless gauge invariance is respected, any attempt at the calculation of circuit QED quantities is bound to diverge. We then present a theoretical approach to the calculation of a finite spontaneous emission rate and the Lamb shift that is free of cutoff.
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Affiliation(s)
- Moein Malekakhlagh
- Department of Electrical Engineering, Princeton University, Princeton, New Jersey 08544, USA
| | - Alexandru Petrescu
- Department of Electrical Engineering, Princeton University, Princeton, New Jersey 08544, USA
| | - Hakan E Türeci
- Department of Electrical Engineering, Princeton University, Princeton, New Jersey 08544, USA
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25
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George RE, Senior J, Saira OP, Pekola JP, de Graaf SE, Lindström T, Pashkin YA. Multiplexing Superconducting Qubit Circuit for Single Microwave Photon Generation. JOURNAL OF LOW TEMPERATURE PHYSICS 2017; 189:60-75. [PMID: 32025044 PMCID: PMC6979489 DOI: 10.1007/s10909-017-1787-x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 12/14/2016] [Accepted: 06/20/2017] [Indexed: 06/10/2023]
Abstract
We report on a device that integrates eight superconducting transmon qubits in λ / 4 superconducting coplanar waveguide resonators fed from a common feedline. Using this multiplexing architecture, each resonator and qubit can be addressed individually, thus reducing the required hardware resources and allowing their individual characterisation by spectroscopic methods. The measured device parameters agree with the designed values, and the resonators and qubits exhibit excellent coherence properties and strong coupling, with the qubit relaxation rate dominated by the Purcell effect when brought in resonance with the resonator. Our analysis shows that the circuit is suitable for generation of single microwave photons on demand with an efficiency exceeding 80%.
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Affiliation(s)
- R. E. George
- Physics Department, Lancaster University, Lancaster, LA1 4YB UK
| | - J. Senior
- Low Temperature Laboratory, Department of Applied Physics, Aalto University School of Science, P.O. Box 13500, 00076 AALTO, Finland
| | - O.-P. Saira
- Low Temperature Laboratory, Department of Applied Physics, Aalto University School of Science, P.O. Box 13500, 00076 AALTO, Finland
| | - J. P. Pekola
- Low Temperature Laboratory, Department of Applied Physics, Aalto University School of Science, P.O. Box 13500, 00076 AALTO, Finland
| | - S. E. de Graaf
- National Physical Laboratory, Hampton Road, Teddington, TW11 0LW UK
| | - T. Lindström
- National Physical Laboratory, Hampton Road, Teddington, TW11 0LW UK
| | - Yu A. Pashkin
- Physics Department, Lancaster University, Lancaster, LA1 4YB UK
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26
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The flux qubit revisited to enhance coherence and reproducibility. Nat Commun 2016; 7:12964. [PMID: 27808092 PMCID: PMC5097147 DOI: 10.1038/ncomms12964] [Citation(s) in RCA: 67] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2015] [Accepted: 08/19/2016] [Indexed: 11/09/2022] Open
Abstract
The scalable application of quantum information science will stand on reproducible and controllable high-coherence quantum bits (qubits). Here, we revisit the design and fabrication of the superconducting flux qubit, achieving a planar device with broad-frequency tunability, strong anharmonicity, high reproducibility and relaxation times in excess of 40 μs at its flux-insensitive point. Qubit relaxation times T1 across 22 qubits are consistently matched with a single model involving resonator loss, ohmic charge noise and 1/f-flux noise, a noise source previously considered primarily in the context of dephasing. We furthermore demonstrate that qubit dephasing at the flux-insensitive point is dominated by residual thermal-photons in the readout resonator. The resulting photon shot noise is mitigated using a dynamical decoupling protocol, resulting in T2≈85 μs, approximately the 2T1 limit. In addition to realizing an improved flux qubit, our results uniquely identify photon shot noise as limiting T2 in contemporary qubits based on transverse qubit–resonator interaction. Scalable quantum information processing requires controllable high-coherence qubits. Here, the authors present superconducting flux qubits with broad frequency tunability, strong anharmonicity and high reproducibility, identifying photon shot noise as the main source of dephasing for further improvements.
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27
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Vool U, Shankar S, Mundhada SO, Ofek N, Narla A, Sliwa K, Zalys-Geller E, Liu Y, Frunzio L, Schoelkopf RJ, Girvin SM, Devoret MH. Continuous Quantum Nondemolition Measurement of the Transverse Component of a Qubit. PHYSICAL REVIEW LETTERS 2016; 117:133601. [PMID: 27715126 DOI: 10.1103/physrevlett.117.133601] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/23/2016] [Indexed: 06/06/2023]
Abstract
Quantum jumps of a qubit are usually observed between its energy eigenstates, also known as its longitudinal pseudospin component. Is it possible, instead, to observe quantum jumps between the transverse superpositions of these eigenstates? We answer positively by presenting the first continuous quantum nondemolition measurement of the transverse component of an individual qubit. In a circuit QED system irradiated by two pump tones, we engineer an effective Hamiltonian whose eigenstates are the transverse qubit states, and a dispersive measurement of the corresponding operator. Such transverse component measurements are a useful tool in the driven-dissipative operation engineering toolbox, which is central to quantum simulation and quantum error correction.
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Affiliation(s)
- U Vool
- Department of Applied Physics and Physics, Yale University, New Haven, Connecticut 06520, USA
| | - S Shankar
- Department of Applied Physics and Physics, Yale University, New Haven, Connecticut 06520, USA
| | - S O Mundhada
- Department of Applied Physics and Physics, Yale University, New Haven, Connecticut 06520, USA
| | - N Ofek
- Department of Applied Physics and Physics, Yale University, New Haven, Connecticut 06520, USA
| | - A Narla
- Department of Applied Physics and Physics, Yale University, New Haven, Connecticut 06520, USA
| | - K Sliwa
- Department of Applied Physics and Physics, Yale University, New Haven, Connecticut 06520, USA
| | - E Zalys-Geller
- Department of Applied Physics and Physics, Yale University, New Haven, Connecticut 06520, USA
| | - Y Liu
- Department of Applied Physics and Physics, Yale University, New Haven, Connecticut 06520, USA
| | - L Frunzio
- Department of Applied Physics and Physics, Yale University, New Haven, Connecticut 06520, USA
| | - R J Schoelkopf
- Department of Applied Physics and Physics, Yale University, New Haven, Connecticut 06520, USA
| | - S M Girvin
- Department of Applied Physics and Physics, Yale University, New Haven, Connecticut 06520, USA
| | - M H Devoret
- Department of Applied Physics and Physics, Yale University, New Haven, Connecticut 06520, USA
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28
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Mapping quantum state dynamics in spontaneous emission. Nat Commun 2016; 7:11527. [PMID: 27167893 PMCID: PMC4865872 DOI: 10.1038/ncomms11527] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2016] [Accepted: 04/05/2016] [Indexed: 11/08/2022] Open
Abstract
The evolution of a quantum state undergoing radiative decay depends on how its emission is detected. If the emission is detected in the form of energy quanta, the evolution is characterized by a quantum jump to a lower energy state. In contrast, detection of the wave nature of the emitted radiation leads to different dynamics. Here, we investigate the diffusive dynamics of a superconducting artificial atom under continuous homodyne detection of its spontaneous emission. Using quantum state tomography, we characterize the correlation between the detected homodyne signal and the emitter's state, and map out the conditional back-action of homodyne measurement. By tracking the diffusive quantum trajectories of the state as it decays, we characterize selective stochastic excitation induced by the choice of measurement basis. Our results demonstrate dramatic differences from the quantum jump evolution associated with photodetection and highlight how continuous field detection can be harnessed to control quantum evolution.
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29
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Didier N, Bourassa J, Blais A. Fast Quantum Nondemolition Readout by Parametric Modulation of Longitudinal Qubit-Oscillator Interaction. PHYSICAL REVIEW LETTERS 2015; 115:203601. [PMID: 26613438 DOI: 10.1103/physrevlett.115.203601] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/27/2015] [Indexed: 06/05/2023]
Abstract
We show how to realize fast and high-fidelity quantum nondemolition qubit readout using longitudinal qubit-oscillator interaction. This is accomplished by modulating the longitudinal coupling at the cavity frequency. The qubit-oscillator interaction then acts as a qubit-state dependent drive on the cavity, a situation that is fundamentally different from the standard dispersive case. Single-mode squeezing can be exploited to exponentially increase the signal-to-noise ratio of this readout protocol. We present an implementation of this longitudinal parametric readout in circuit quantum electrodynamics and a possible multiqubit architecture.
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Affiliation(s)
- Nicolas Didier
- Department of Physics, McGill University, 3600 rue University, Montreal, Quebec H3A 2T8, Canada
- Départment de Physique, Université de Sherbrooke, 2500 boulevard de l'Université, Sherbrooke, Québec J1K 2R1, Canada
| | - Jérôme Bourassa
- Cégep de Granby, 235, rue Saint-Jacques, Granby, Québec J2G 9H7, Canada
| | - Alexandre Blais
- Départment de Physique, Université de Sherbrooke, 2500 boulevard de l'Université, Sherbrooke, Québec J1K 2R1, Canada
- Canadian Institute for Advanced Research, Toronto, Ontario M5G 1Z8, Canada
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30
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Herrera-Martí DA, Gefen T, Aharonov D, Katz N, Retzker A. Quantum Error-Correction-Enhanced Magnetometer Overcoming the Limit Imposed by Relaxation. PHYSICAL REVIEW LETTERS 2015; 115:200501. [PMID: 26613424 DOI: 10.1103/physrevlett.115.200501] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/30/2014] [Indexed: 06/05/2023]
Abstract
When incorporated in quantum sensing protocols, quantum error correction can be used to correct for high frequency noise, as the correction procedure does not depend on the actual shape of the noise spectrum. As such, it provides a powerful way to complement usual refocusing techniques. Relaxation imposes a fundamental limit on the sensitivity of state of the art quantum sensors which cannot be overcome by dynamical decoupling. The only way to overcome this is to utilize quantum error correcting codes. We present a superconducting magnetometry design that incorporates approximate quantum error correction, in which the signal is generated by a two qubit Hamiltonian term. This two-qubit term is provided by the dynamics of a tunable coupler between two transmon qubits. For fast enough correction, it is possible to lengthen the coherence time of the device beyond the relaxation limit.
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Affiliation(s)
- David A Herrera-Martí
- Racah Institute of Physics, The Hebrew University of Jerusalem, Jerusalem 91904, Givat Ram, Israel
| | - Tuvia Gefen
- Racah Institute of Physics, The Hebrew University of Jerusalem, Jerusalem 91904, Givat Ram, Israel
| | - Dorit Aharonov
- School of Computer Science and Engineering, The Hebrew University, Jerusalem 91904, Israel
| | - Nadav Katz
- Racah Institute of Physics, The Hebrew University of Jerusalem, Jerusalem 91904, Givat Ram, Israel
| | - Alex Retzker
- Racah Institute of Physics, The Hebrew University of Jerusalem, Jerusalem 91904, Givat Ram, Israel
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31
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Larsen TW, Petersson KD, Kuemmeth F, Jespersen TS, Krogstrup P, Nygård J, Marcus CM. Semiconductor-Nanowire-Based Superconducting Qubit. PHYSICAL REVIEW LETTERS 2015; 115:127001. [PMID: 26431009 DOI: 10.1103/physrevlett.115.127001] [Citation(s) in RCA: 99] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/28/2015] [Indexed: 06/05/2023]
Abstract
We introduce a hybrid qubit based on a semiconductor nanowire with an epitaxially grown superconductor layer. Josephson energy of the transmonlike device ("gatemon") is controlled by an electrostatic gate that depletes carriers in a semiconducting weak link region. Strong coupling to an on-chip microwave cavity and coherent qubit control via gate voltage pulses is demonstrated, yielding reasonably long relaxation times (~0.8 μs) and dephasing times (~1 μs), exceeding gate operation times by 2 orders of magnitude, in these first-generation devices. Because qubit control relies on voltages rather than fluxes, dissipation in resistive control lines is reduced, screening reduces cross talk, and the absence of flux control allows operation in a magnetic field, relevant for topological quantum information.
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Affiliation(s)
- T W Larsen
- Center for Quantum Devices, Niels Bohr Institute, University of Copenhagen, Copenhagen 2100, Denmark
| | - K D Petersson
- Center for Quantum Devices, Niels Bohr Institute, University of Copenhagen, Copenhagen 2100, Denmark
| | - F Kuemmeth
- Center for Quantum Devices, Niels Bohr Institute, University of Copenhagen, Copenhagen 2100, Denmark
| | - T S Jespersen
- Center for Quantum Devices, Niels Bohr Institute, University of Copenhagen, Copenhagen 2100, Denmark
| | - P Krogstrup
- Center for Quantum Devices, Niels Bohr Institute, University of Copenhagen, Copenhagen 2100, Denmark
| | - J Nygård
- Center for Quantum Devices, Niels Bohr Institute, University of Copenhagen, Copenhagen 2100, Denmark
- Nano-Science Center, Niels Bohr Institute, University of Copenhagen, Copenhagen 2100, Denmark
| | - C M Marcus
- Center for Quantum Devices, Niels Bohr Institute, University of Copenhagen, Copenhagen 2100, Denmark
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32
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Didier N, Kamal A, Oliver WD, Blais A, Clerk AA. Heisenberg-Limited Qubit Read-Out with Two-Mode Squeezed Light. PHYSICAL REVIEW LETTERS 2015; 115:093604. [PMID: 26371653 DOI: 10.1103/physrevlett.115.093604] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/06/2015] [Indexed: 06/05/2023]
Abstract
We show how to use two-mode squeezed light to exponentially enhance cavity-based dispersive qubit measurement. Our scheme enables true Heisenberg-limited scaling of the measurement, and crucially, it is not restricted to small dispersive couplings or unrealistically long measurement times. It involves coupling a qubit dispersively to two cavities and making use of a symmetry in the dynamics of joint cavity quadratures (a so-called quantum-mechanics-free subsystem). We discuss the basic scaling of the scheme and its robustness against imperfections, as well as a realistic implementation in circuit quantum electrodynamics.
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Affiliation(s)
- Nicolas Didier
- Department of Physics, McGill University, 3600 rue University, Montreal, Quebec H3A 2T8, Canada
- Départment de Physique, Université de Sherbrooke, 2500 boulevard de l'Université, Sherbrooke, Québec J1K 2R1, Canada
| | - Archana Kamal
- Research Laboratory of Electronics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
| | - William D Oliver
- Research Laboratory of Electronics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
- MIT Lincoln Laboratory, 244 Wood Street, Lexington, Massachusetts 02420, USA
| | - Alexandre Blais
- Départment de Physique, Université de Sherbrooke, 2500 boulevard de l'Université, Sherbrooke, Québec J1K 2R1, Canada
- Canadian Institute for Advanced Research, Toronto, Ontario M5G 1Z8, Canada
| | - Aashish A Clerk
- Department of Physics, McGill University, 3600 rue University, Montreal, Quebec H3A 2T8, Canada
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33
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McKay DC, Naik R, Reinhold P, Bishop LS, Schuster DI. High-contrast qubit interactions using multimode cavity QED. PHYSICAL REVIEW LETTERS 2015; 114:080501. [PMID: 25768741 DOI: 10.1103/physrevlett.114.080501] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/07/2014] [Indexed: 06/04/2023]
Abstract
We introduce a new multimode cavity QED architecture for superconducting circuits that can be used to implement photonic memories, more efficient Purcell filters, and quantum simulations of photonic materials. We show that qubit interactions mediated by multimode cavities can have exponentially improved contrast for two qubit gates without sacrificing gate speed. Using two qubits coupled via a three-mode cavity system we spectroscopically observe multimode strong couplings up to 102 MHz and demonstrate suppressed interactions off resonance of 10 kHz when the qubits are ≈600 MHz detuned from the cavity resonance. We study Landau-Zener transitions in our multimode systems and demonstrate quasiadiabatic loading of single photons into the multimode cavity in 25 ns. We introduce an adiabatic gate protocol to realize a controlled-Z gate between the qubits in 95 ns and create a Bell state with 94.7% fidelity. This corresponds to an on/off ratio (gate contrast) of 1000.
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Affiliation(s)
- David C McKay
- James Franck Institute and Department of Physics, University of Chicago, Chicago, Illinois 60637, USA
| | - Ravi Naik
- James Franck Institute and Department of Physics, University of Chicago, Chicago, Illinois 60637, USA
| | - Philip Reinhold
- James Franck Institute and Department of Physics, University of Chicago, Chicago, Illinois 60637, USA
| | - Lev S Bishop
- Condensed Matter Theory Center, Department of Physics, University of Maryland, College Park, Maryland 20742, USA
- IBM T.J. Watson Research Center, Yorktown Heights, New York 10598, USA
| | - David I Schuster
- James Franck Institute and Department of Physics, University of Chicago, Chicago, Illinois 60637, USA
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34
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Peterer MJ, Bader SJ, Jin X, Yan F, Kamal A, Gudmundsen TJ, Leek PJ, Orlando TP, Oliver WD, Gustavsson S. Coherence and decay of higher energy levels of a superconducting transmon qubit. PHYSICAL REVIEW LETTERS 2015; 114:010501. [PMID: 25615454 DOI: 10.1103/physrevlett.114.010501] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/11/2014] [Indexed: 06/04/2023]
Abstract
We present measurements of coherence and successive decay dynamics of higher energy levels of a superconducting transmon qubit. By applying consecutive π pulses for each sequential transition frequency, we excite the qubit from the ground state up to its fourth excited level and characterize the decay and coherence of each state. We find the decay to proceed mainly sequentially, with relaxation times in excess of 20 μs for all transitions. We also provide a direct measurement of the charge dispersion of these levels by analyzing beating patterns in Ramsey fringes. The results demonstrate the feasibility of using higher levels in transmon qubits for encoding quantum information.
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Affiliation(s)
- Michael J Peterer
- Research Laboratory of Electronics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA and Clarendon Laboratory, Department of Physics, University of Oxford, OX1 3PU Oxford, United Kingdom
| | - Samuel J Bader
- Research Laboratory of Electronics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
| | - Xiaoyue Jin
- Research Laboratory of Electronics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
| | - Fei Yan
- Research Laboratory of Electronics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
| | - Archana Kamal
- Research Laboratory of Electronics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
| | | | - Peter J Leek
- Clarendon Laboratory, Department of Physics, University of Oxford, OX1 3PU Oxford, United Kingdom
| | - Terry P Orlando
- Research Laboratory of Electronics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
| | - William D Oliver
- Research Laboratory of Electronics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA and MIT Lincoln Laboratory, 244 Wood Street, Lexington, Massachusetts 02420, USA
| | - Simon Gustavsson
- Research Laboratory of Electronics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
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35
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Controllable microwave three-wave mixing via a single three-level superconducting quantum circuit. Sci Rep 2014; 4:7289. [PMID: 25487352 PMCID: PMC5376979 DOI: 10.1038/srep07289] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2014] [Accepted: 11/07/2014] [Indexed: 11/09/2022] Open
Abstract
Three-wave mixing in second-order nonlinear optical processes cannot occur in atomic systems due to the electric-dipole selection rules. In contrast, we demonstrate that second-order nonlinear processes can occur in a superconducting quantum circuit (i.e., a superconducting artificial atom) when the inversion symmetry of the potential energy is broken by simply changing the applied magnetic flux. In particular, we show that difference- and sum-frequencies (and second harmonics) can be generated in the microwave regime in a controllable manner by using a single three-level superconducting flux quantum circuit (SFQC). For our proposed parameters, the frequency tunability of this circuit can be achieved in the range of about 17 GHz for the sum-frequency generation, and around 42 GHz (or 26 GHz) for the difference-frequency generation. Our proposal provides a simple method to generate second-order nonlinear processes within current experimental parameters of SFQCs.
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36
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Stern M, Catelani G, Kubo Y, Grezes C, Bienfait A, Vion D, Esteve D, Bertet P. Flux qubits with long coherence times for hybrid quantum circuits. PHYSICAL REVIEW LETTERS 2014; 113:123601. [PMID: 25279628 DOI: 10.1103/physrevlett.113.123601] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/03/2014] [Indexed: 06/03/2023]
Abstract
We present measurements of superconducting flux qubits embedded in a three dimensional copper cavity. The qubits are fabricated on a sapphire substrate and are measured by coupling them inductively to an on-chip superconducting resonator located in the middle of the cavity. At their flux-insensitive point, all measured qubits reach an intrinsic energy relaxation time in the 6-20 μs range and a pure dephasing time comprised between 3 and 10 μs. This significant improvement over previous works opens the way to the coherent coupling of a flux qubit to individual spins.
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Affiliation(s)
- M Stern
- Quantronics Group, SPEC, IRAMIS, DSM, CEA Saclay, 91191 Gif-sur-Yvette, France
| | - G Catelani
- Forschungszentrum Jülich, Peter Grünberg Institut (PGI-2), 52425 Jülich, Germany
| | - Y Kubo
- Quantronics Group, SPEC, IRAMIS, DSM, CEA Saclay, 91191 Gif-sur-Yvette, France
| | - C Grezes
- Quantronics Group, SPEC, IRAMIS, DSM, CEA Saclay, 91191 Gif-sur-Yvette, France
| | - A Bienfait
- Quantronics Group, SPEC, IRAMIS, DSM, CEA Saclay, 91191 Gif-sur-Yvette, France
| | - D Vion
- Quantronics Group, SPEC, IRAMIS, DSM, CEA Saclay, 91191 Gif-sur-Yvette, France
| | - D Esteve
- Quantronics Group, SPEC, IRAMIS, DSM, CEA Saclay, 91191 Gif-sur-Yvette, France
| | - P Bertet
- Quantronics Group, SPEC, IRAMIS, DSM, CEA Saclay, 91191 Gif-sur-Yvette, France
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37
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Ginossar E, Grosfeld E. Microwave transitions as a signature of coherent parity mixing effects in the Majorana-transmon qubit. Nat Commun 2014; 5:4772. [DOI: 10.1038/ncomms5772] [Citation(s) in RCA: 50] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2014] [Accepted: 07/22/2014] [Indexed: 11/09/2022] Open
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38
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Shankar S, Hatridge M, Leghtas Z, Sliwa KM, Narla A, Vool U, Girvin SM, Frunzio L, Mirrahimi M, Devoret MH. Autonomously stabilized entanglement between two superconducting quantum bits. Nature 2013; 504:419-22. [PMID: 24270808 DOI: 10.1038/nature12802] [Citation(s) in RCA: 234] [Impact Index Per Article: 21.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2013] [Accepted: 10/22/2013] [Indexed: 12/27/2022]
Abstract
Quantum error correction codes are designed to protect an arbitrary state of a multi-qubit register from decoherence-induced errors, but their implementation is an outstanding challenge in the development of large-scale quantum computers. The first step is to stabilize a non-equilibrium state of a simple quantum system, such as a quantum bit (qubit) or a cavity mode, in the presence of decoherence. This has recently been accomplished using measurement-based feedback schemes. The next step is to prepare and stabilize a state of a composite system. Here we demonstrate the stabilization of an entangled Bell state of a quantum register of two superconducting qubits for an arbitrary time. Our result is achieved using an autonomous feedback scheme that combines continuous drives along with a specifically engineered coupling between the two-qubit register and a dissipative reservoir. Similar autonomous feedback techniques have been used for qubit reset, single-qubit state stabilization, and the creation and stabilization of states of multipartite quantum systems. Unlike conventional, measurement-based schemes, the autonomous approach uses engineered dissipation to counteract decoherence, obviating the need for a complicated external feedback loop to correct errors. Instead, the feedback loop is built into the Hamiltonian such that the steady state of the system in the presence of drives and dissipation is a Bell state, an essential building block for quantum information processing. Such autonomous schemes, which are broadly applicable to a variety of physical systems, as demonstrated by the accompanying paper on trapped ion qubits, will be an essential tool for the implementation of quantum error correction.
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Affiliation(s)
- S Shankar
- Department of Applied Physics and Physics, Yale University, New Haven, Connecticut 06520, USA
| | - M Hatridge
- Department of Applied Physics and Physics, Yale University, New Haven, Connecticut 06520, USA
| | - Z Leghtas
- Department of Applied Physics and Physics, Yale University, New Haven, Connecticut 06520, USA
| | - K M Sliwa
- Department of Applied Physics and Physics, Yale University, New Haven, Connecticut 06520, USA
| | - A Narla
- Department of Applied Physics and Physics, Yale University, New Haven, Connecticut 06520, USA
| | - U Vool
- Department of Applied Physics and Physics, Yale University, New Haven, Connecticut 06520, USA
| | - S M Girvin
- Department of Applied Physics and Physics, Yale University, New Haven, Connecticut 06520, USA
| | - L Frunzio
- Department of Applied Physics and Physics, Yale University, New Haven, Connecticut 06520, USA
| | - M Mirrahimi
- 1] Department of Applied Physics and Physics, Yale University, New Haven, Connecticut 06520, USA [2] INRIA Paris-Rocquencourt, Domaine de Voluceau, BP 105, 78153 Le Chesnay Cedex, France
| | - M H Devoret
- Department of Applied Physics and Physics, Yale University, New Haven, Connecticut 06520, USA
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39
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Deterministic entanglement of superconducting qubits by parity measurement and feedback. Nature 2013; 502:350-4. [DOI: 10.1038/nature12513] [Citation(s) in RCA: 226] [Impact Index Per Article: 20.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2013] [Accepted: 07/24/2013] [Indexed: 12/25/2022]
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40
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de Graaf SE, Leppäkangas J, Adamyan A, Danilov AV, Lindström T, Fogelström M, Bauch T, Johansson G, Kubatkin SE. Charge qubit coupled to an intense microwave electromagnetic field in a superconducting Nb device: evidence for photon-assisted quasiparticle tunneling. PHYSICAL REVIEW LETTERS 2013; 111:137002. [PMID: 24116809 DOI: 10.1103/physrevlett.111.137002] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/29/2013] [Indexed: 06/02/2023]
Abstract
We study a superconducting charge qubit coupled to an intensive electromagnetic field and probe changes in the resonance frequency of the formed dressed states. At large driving strengths, exceeding the qubit energy-level splitting, this reveals the well known Landau-Zener-Stückelberg interference structure of a longitudinally driven two-level system. For even stronger drives, we observe a significant change in the Landau-Zener-Stückelberg pattern and contrast. We attribute this to photon-assisted quasiparticle tunneling in the qubit. This results in the recovery of the qubit parity, eliminating effects of quasiparticle poisoning, and leads to an enhanced interferometric response. The interference pattern becomes robust to quasiparticle poisoning and has a good potential for accurate charge sensing.
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Affiliation(s)
- S E de Graaf
- Department of Microtechnology and Nanoscience, MC2, Chalmers University of Technology, SE-41296 Goteborg, Sweden
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41
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Barends R, Kelly J, Megrant A, Sank D, Jeffrey E, Chen Y, Yin Y, Chiaro B, Mutus J, Neill C, O'Malley P, Roushan P, Wenner J, White TC, Cleland AN, Martinis JM. Coherent Josephson qubit suitable for scalable quantum integrated circuits. PHYSICAL REVIEW LETTERS 2013; 111:080502. [PMID: 24010421 DOI: 10.1103/physrevlett.111.080502] [Citation(s) in RCA: 55] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/05/2013] [Indexed: 06/02/2023]
Abstract
We demonstrate a planar, tunable superconducting qubit with energy relaxation times up to 44 μs. This is achieved by using a geometry designed to both minimize radiative loss and reduce coupling to materials-related defects. At these levels of coherence, we find a fine structure in the qubit energy lifetime as a function of frequency, indicating the presence of a sparse population of incoherent, weakly coupled two-level defects. We elucidate this defect physics by experimentally varying the geometry and by a model analysis. Our "Xmon" qubit combines facile fabrication, straightforward connectivity, fast control, and long coherence, opening a viable route to constructing a chip-based quantum computer.
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Affiliation(s)
- R Barends
- Department of Physics, University of California, Santa Barbara, California 93106, USA
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42
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Devoret MH, Schoelkopf RJ. Superconducting Circuits for Quantum Information: An Outlook. Science 2013; 339:1169-74. [DOI: 10.1126/science.1231930] [Citation(s) in RCA: 1301] [Impact Index Per Article: 118.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
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43
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Ristè D, Bultink CC, Tiggelman MJ, Schouten RN, Lehnert KW, DiCarlo L. Millisecond charge-parity fluctuations and induced decoherence in a superconducting transmon qubit. Nat Commun 2013; 4:1913. [PMID: 23715272 PMCID: PMC3674283 DOI: 10.1038/ncomms2936] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2013] [Accepted: 04/29/2013] [Indexed: 11/24/2022] Open
Abstract
The tunnelling of quasiparticles across Josephson junctions in superconducting quantum circuits is an intrinsic decoherence mechanism for qubit degrees of freedom. Understanding the limits imposed by quasiparticle tunnelling on qubit relaxation and dephasing is of theoretical and experimental interest, particularly as improved understanding of extrinsic mechanisms has allowed crossing the 100 microsecond mark in transmon-type charge qubits. Here, by integrating recent developments in high-fidelity qubit readout and feedback control in circuit quantum electrodynamics, we transform a state-of-the-art transmon into its own real-time charge-parity detector. We directly measure the tunnelling of quasiparticles across the single junction and isolate the contribution of this tunnelling to qubit relaxation and dephasing, without reliance on theory. The millisecond timescales measured demonstrate that quasiparticle tunnelling does not presently bottleneck transmon qubit coherence, leaving room for yet another order of magnitude increase.
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Affiliation(s)
- D. Ristè
- Kavli Institute of Nanoscience, Delft University of Technology, PO Box 5046, 2600 GA Delft, The Netherlands
| | - C. C. Bultink
- Kavli Institute of Nanoscience, Delft University of Technology, PO Box 5046, 2600 GA Delft, The Netherlands
| | - M. J. Tiggelman
- Kavli Institute of Nanoscience, Delft University of Technology, PO Box 5046, 2600 GA Delft, The Netherlands
| | - R. N. Schouten
- Kavli Institute of Nanoscience, Delft University of Technology, PO Box 5046, 2600 GA Delft, The Netherlands
| | - K. W. Lehnert
- JILA, National Institute of Standards and Technology and Department of Physics, University of Colorado, Boulder, Colorado 80309, USA
| | - L. DiCarlo
- Kavli Institute of Nanoscience, Delft University of Technology, PO Box 5046, 2600 GA Delft, The Netherlands
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44
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Ristè D, van Leeuwen JG, Ku HS, Lehnert KW, DiCarlo L. Initialization by measurement of a superconducting quantum bit circuit. PHYSICAL REVIEW LETTERS 2012; 109:050507. [PMID: 23006158 DOI: 10.1103/physrevlett.109.050507] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/05/2012] [Indexed: 06/01/2023]
Abstract
We demonstrate initialization by joint measurement of two transmon qubits in 3D circuit quantum electrodynamics. Homodyne detection of cavity transmission is enhanced by Josephson parametric amplification to discriminate the two-qubit ground state from single-qubit excitations nondestructively and with 98.1% fidelity. Measurement and postselection of a steady-state mixture with 4.7% residual excitation per qubit achieve 98.8% fidelity to the ground state, thus outperforming passive initialization.
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Affiliation(s)
- D Ristè
- Kavli Institute of Nanoscience, Delft University of Technology, The Netherlands
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45
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Nigg SE, Paik H, Vlastakis B, Kirchmair G, Shankar S, Frunzio L, Devoret MH, Schoelkopf RJ, Girvin SM. Black-box superconducting circuit quantization. PHYSICAL REVIEW LETTERS 2012; 108:240502. [PMID: 23004246 DOI: 10.1103/physrevlett.108.240502] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/03/2012] [Indexed: 06/01/2023]
Abstract
We present a semiclassical method for determining the effective low-energy quantum Hamiltonian of weakly anharmonic superconducting circuits containing mesoscopic Josephson junctions coupled to electromagnetic environments made of an arbitrary combination of distributed and lumped elements. A convenient basis, capturing the multimode physics, is given by the quantized eigenmodes of the linearized circuit and is fully determined by a classical linear response function. The method is used to calculate numerically the low-energy spectrum of a 3D transmon system, and quantitative agreement with measurements is found.
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Affiliation(s)
- Simon E Nigg
- Department of Physics, Yale University, New Haven, Connecticut 06520, USA
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46
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Sun L, DiCarlo L, Reed MD, Catelani G, Bishop LS, Schuster DI, Johnson BR, Yang GA, Frunzio L, Glazman L, Devoret MH, Schoelkopf RJ. Measurements of quasiparticle tunneling dynamics in a band-gap-engineered transmon qubit. PHYSICAL REVIEW LETTERS 2012; 108:230509. [PMID: 23003936 DOI: 10.1103/physrevlett.108.230509] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/11/2011] [Indexed: 06/01/2023]
Abstract
We have engineered the band gap profile of transmon qubits by combining oxygen-doped Al for tunnel junction electrodes and clean Al as quasiparticle traps to investigate energy relaxation due to quasiparticle tunneling. The relaxation time T1 of the qubits is shown to be insensitive to this band gap engineering. Operating at relatively low-E(J)/E(C) makes the transmon transition frequency distinctly dependent on the charge parity, allowing us to detect the quasiparticles tunneling across the qubit junction. Quasiparticle kinetics have been studied by monitoring the frequency switching due to even-odd parity change in real time. It shows the switching time is faster than 10 μs, indicating quasiparticle-induced relaxation has to be reduced to achieve T1 much longer than 100 μs.
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Affiliation(s)
- L Sun
- Department of Physics and Applied Physics, Yale University, New Haven, Connecticut 06520, USA
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47
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Kim MD, Moon K. Readout of superconducting flux qubit state with a Cooper pair box. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2012; 24:225305. [PMID: 22585418 DOI: 10.1088/0953-8984/24/22/225305] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
We study a readout scheme of a superconducting flux qubit state with a Cooper pair box as a transmon. The qubit states consist of the superpositions of two degenerate states where the charge and phase degrees of freedom are entangled. Owing to the robustness of the transmon against external fluctuations, our readout scheme enables the quantum non-demolition and single-shot measurement of flux qubit states. The qubit state readout can be performed by using the nonlinear Josephson amplifiers after a π/2 rotation driven by an ac electric field.
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Affiliation(s)
- Mun Dae Kim
- Institute of Physics and Applied Physics, Yonsei University, Seoul, Korea.
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48
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Gustavsson S, Bylander J, Yan F, Forn-Díaz P, Bolkhovsky V, Braje D, Fitch G, Harrabi K, Lennon D, Miloshi J, Murphy P, Slattery R, Spector S, Turek B, Weir T, Welander PB, Yoshihara F, Cory DG, Nakamura Y, Orlando TP, Oliver WD. Driven dynamics and rotary echo of a qubit tunably coupled to a harmonic oscillator. PHYSICAL REVIEW LETTERS 2012; 108:170503. [PMID: 22680846 DOI: 10.1103/physrevlett.108.170503] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/07/2011] [Indexed: 06/01/2023]
Abstract
We have investigated the driven dynamics of a superconducting flux qubit that is tunably coupled to a microwave resonator. We find that the qubit experiences an oscillating field mediated by off-resonant driving of the resonator, leading to strong modifications of the qubit Rabi frequency. This opens an additional noise channel, and we find that low-frequency noise in the coupling parameter causes a reduction of the coherence time during driven evolution. The noise can be mitigated with the rotary-echo pulse sequence, which, for driven systems, is analogous to the Hahn-echo sequence.
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Affiliation(s)
- S Gustavsson
- Research Laboratory of Electronics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
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49
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Paik H, Schuster DI, Bishop LS, Kirchmair G, Catelani G, Sears AP, Johnson BR, Reagor MJ, Frunzio L, Glazman LI, Girvin SM, Devoret MH, Schoelkopf RJ. Observation of high coherence in Josephson junction qubits measured in a three-dimensional circuit QED architecture. PHYSICAL REVIEW LETTERS 2011; 107:240501. [PMID: 22242979 DOI: 10.1103/physrevlett.107.240501] [Citation(s) in RCA: 85] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/03/2011] [Revised: 09/15/2011] [Indexed: 05/27/2023]
Abstract
Superconducting quantum circuits based on Josephson junctions have made rapid progress in demonstrating quantum behavior and scalability. However, the future prospects ultimately depend upon the intrinsic coherence of Josephson junctions, and whether superconducting qubits can be adequately isolated from their environment. We introduce a new architecture for superconducting quantum circuits employing a three-dimensional resonator that suppresses qubit decoherence while maintaining sufficient coupling to the control signal. With the new architecture, we demonstrate that Josephson junction qubits are highly coherent, with T2 ∼ 10 to 20 μs without the use of spin echo, and highly stable, showing no evidence for 1/f critical current noise. These results suggest that the overall quality of Josephson junctions in these qubits will allow error rates of a few 10(-4), approaching the error correction threshold.
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Affiliation(s)
- Hanhee Paik
- Department of Physics and Applied Physics, Yale University, New Haven, Connecticut 06520, USA
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50
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Kim Z, Suri B, Zaretskey V, Novikov S, Osborn KD, Mizel A, Wellstood FC, Palmer BS. Decoupling a Cooper-pair box to enhance the lifetime to 0.2 ms. PHYSICAL REVIEW LETTERS 2011; 106:120501. [PMID: 21517289 DOI: 10.1103/physrevlett.106.120501] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/21/2010] [Indexed: 05/30/2023]
Abstract
We present results on a circuit QED experiment in which a separate transmission line is used to address a quasilumped element superconducting microwave resonator which is in turn coupled to an Al/AlO(x)/Al Cooper-pair box charge qubit. With our device, we find a strong correlation between the lifetime of the qubit and the inverse of the coupling between the qubit and the transmission line. At the smallest coupling we measured, the lifetime of the Cooper-pair box was T₁=200 μs, which represents more than a twentyfold improvement in the lifetime of the Cooper-pair box compared with previous results. These results imply that the loss tangent in the AlO(x) junction barrier must be less than about 4×10⁻⁸ at 4.5 GHz, about 4 orders of magnitude less than reported in larger area Al/AlO(x)/Al tunnel junctions.
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Affiliation(s)
- Z Kim
- Laboratory for Physical Sciences, College Park, Maryland 20740, USA
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