1
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Kondappan M, Ivannikov V, Byrnes T. Optical circuit compactification for ultracold atoms. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2024; 95:013004. [PMID: 38265277 DOI: 10.1063/5.0180938] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/13/2023] [Accepted: 12/23/2023] [Indexed: 01/25/2024]
Abstract
We develop a modular and compactified optical circuit for the generation of optical beams for cooling, imaging, and controlling ultracold atoms. One of the simplifications that is made in our circuit is to admix the repumping beams to each other optical beams in its dedicated single-mode fiber. We implement our design, characterize the output, and show that the optical power efficiency of the circuit is in the region of 97%, and after fiber coupling, the efficiencies are in the range of 62-85%. Given its compact design and controllable optical sources, this setup should be adaptable to a variety of quantum experiments based on ultracold gases.
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Affiliation(s)
- Manikandan Kondappan
- State Key Laboratory of Precision Spectroscopy, School of Physical and Material Sciences, East China Normal University, Shanghai 200062, China
- New York University Shanghai, 567 West Yangsi Road, Pudong New District, Shanghai 200126, China
| | - Valentin Ivannikov
- New York University Shanghai, 567 West Yangsi Road, Pudong New District, Shanghai 200126, China
- NYU-ECNU Institute of Physics at NYU Shanghai, 3663 Zhongshan Road North, Shanghai 200062, China
| | - Tim Byrnes
- State Key Laboratory of Precision Spectroscopy, School of Physical and Material Sciences, East China Normal University, Shanghai 200062, China
- Shanghai Frontiers Science Center of Artificial Intelligence and Deep Learning, NYU-ECNU Institute of Physics at NYU Shanghai, New York University Shanghai, 567 West Yangsi Road, Pudong New District, Shanghai 200126, China
- Center for Quantum and Topological Systems (CQTS), NYUAD Research Institute, New York University Abu Dhabi, Abu Dhabi, United Arab Emirates
- Department of Physics, New York University, New York, New York 10003, USA
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2
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Salimian S, Tavassoly MK, Ghasemi M. Multistage entanglement swapping using superconducting qubits in the absence and presence of dissipative environment without Bell state measurement. Sci Rep 2023; 13:16342. [PMID: 37770646 PMCID: PMC10539405 DOI: 10.1038/s41598-023-43592-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2023] [Accepted: 09/26/2023] [Indexed: 09/30/2023] Open
Abstract
In recent decades the entangled state generation is of great importance in the quantum information processing and technologies. In this paper, producing the distributed entangled state of superconducting (SC) qubits is considered using an entanglement swapping protocol in three successive stages. The SC qubit pairs [Formula: see text] with [Formula: see text], where each pair of the qubits has been placed on a separate chip, are initially prepared in maximally entangled states. The external magnetic fields on capacitively coupled pairs [Formula: see text] and [Formula: see text] are implemented for modulating the frequency of qubits. Then, the SC qubits [Formula: see text] and [Formula: see text] are converted into entangled states via operating proper measurements instead of Bell state measurement (which is generally a hard task). Finally, the distributed entangled state of target SC qubits [Formula: see text] can be obtained by applying external magnetic fields on qubits [Formula: see text] and via operating suitable measurements. This process is studied in the absence and presence of thermal decoherence effects. The concurrence, as a measure of entanglement between two target qubits, success probability of the distributed entangled states and the corresponding fidelities are evaluated, by which we find that the state of target SC qubits [Formula: see text] is converted to Bell state with maximum entanglement at some moments of time. Under appropriate conditions the maximum of success probability of the obtained states in each stage approaches 1. However, the maxima of concurrence and success probability gradually decrease due to the thermal noise as time goes on. Moreover, compelling amounts of fidelity, success probability and entanglement can be obtained for the achieved entangled states.
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Affiliation(s)
- S Salimian
- Laser and Optics Group, Faculty of Physics, Yazd University, Yazd, Iran
| | - M K Tavassoly
- Laser and Optics Group, Faculty of Physics, Yazd University, Yazd, Iran.
| | - M Ghasemi
- Laser and Optics Group, Faculty of Physics, Yazd University, Yazd, Iran
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3
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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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4
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Abbasi M, Chen W, Naghiloo M, Joglekar YN, Murch KW. Topological Quantum State Control through Exceptional-Point Proximity. PHYSICAL REVIEW LETTERS 2022; 128:160401. [PMID: 35522514 DOI: 10.1103/physrevlett.128.160401] [Citation(s) in RCA: 12] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/10/2021] [Revised: 01/12/2022] [Accepted: 03/22/2022] [Indexed: 06/14/2023]
Abstract
We study the quantum evolution of a non-Hermitian qubit realized as a submanifold of a dissipative superconducting transmon circuit. Real-time tuning of the system parameters to encircle an exceptional point results in nonreciprocal quantum state transfer. We further observe chiral geometric phases accumulated under state transport, verifying the quantum coherent nature of the evolution in the complex energy landscape and distinguishing between coherent and incoherent effects associated with exceptional point encircling. Our work demonstrates an entirely new method for control over quantum state vectors, highlighting new facets of quantum bath engineering enabled through dynamical non-Hermitian control.
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Affiliation(s)
- Maryam Abbasi
- Department of Physics, Washington University, St. Louis, Missouri 63130, USA
| | - Weijian Chen
- Department of Physics, Washington University, St. Louis, Missouri 63130, USA
- Center for Quantum Sensors, Washington University, St. Louis, Missouri 63130, USA
| | - Mahdi Naghiloo
- Department of Physics, Washington University, St. Louis, Missouri 63130, USA
- Research Laboratory of Electronics, MIT, Cambridge, Massachusetts 02139, USA
| | - Yogesh N Joglekar
- Department of Physics, Indiana University Purdue University Indianapolis (IUPUI), Indianapolis, Indiana 46202, USA
| | - Kater W Murch
- Department of Physics, Washington University, St. Louis, Missouri 63130, USA
- Center for Quantum Sensors, Washington University, St. Louis, Missouri 63130, USA
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5
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Yan H, Zhong Y, Chang HS, Bienfait A, Chou MH, Conner CR, Dumur É, Grebel J, Povey RG, Cleland AN. Entanglement Purification and Protection in a Superconducting Quantum Network. PHYSICAL REVIEW LETTERS 2022; 128:080504. [PMID: 35275688 DOI: 10.1103/physrevlett.128.080504] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/22/2021] [Accepted: 01/10/2022] [Indexed: 06/14/2023]
Abstract
High-fidelity quantum entanglement is a key resource for quantum communication and distributed quantum computing, enabling quantum state teleportation, dense coding, and quantum encryption. Any sources of decoherence in the communication channel, however, degrade entanglement fidelity, thereby increasing the error rates of entangled state protocols. Entanglement purification provides a method to alleviate these nonidealities by distilling impure states into higher-fidelity entangled states. Here we demonstrate the entanglement purification of Bell pairs shared between two remote superconducting quantum nodes connected by a moderately lossy, 1-meter long superconducting communication cable. We use a purification process to correct the dominant amplitude damping errors caused by transmission through the cable, with fractional increases in fidelity as large as 25%, achieved for higher damping errors. The best final fidelity the purification achieves is 94.09±0.98%. In addition, we use both dynamical decoupling and Rabi driving to protect the entangled states from local noise, increasing the effective qubit dephasing time by a factor of 4, from 3 to 12 μs. These methods demonstrate the potential for the generation and preservation of very high-fidelity entanglement in a superconducting quantum communication network.
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Affiliation(s)
- Haoxiong Yan
- Pritzker School of Molecular Engineering, University of Chicago, Chicago, Illinois 60637, USA
| | - Youpeng Zhong
- Pritzker School of Molecular Engineering, University of Chicago, Chicago, Illinois 60637, USA
| | - Hung-Shen Chang
- Pritzker School of Molecular Engineering, University of Chicago, Chicago, Illinois 60637, USA
| | - Audrey Bienfait
- Pritzker School of Molecular Engineering, University of Chicago, Chicago, Illinois 60637, USA
| | - Ming-Han Chou
- Pritzker School of Molecular Engineering, University of Chicago, Chicago, Illinois 60637, USA
- Department of Physics, University of Chicago, Chicago, Illinois 60637, USA
| | - Christopher R Conner
- Pritzker School of Molecular Engineering, University of Chicago, Chicago, Illinois 60637, USA
| | - Étienne Dumur
- Pritzker School of Molecular Engineering, University of Chicago, Chicago, Illinois 60637, USA
- Center for Molecular Engineering and Material Science Division, Argonne National Laboratory, Lemont, Illinois 60439, USA
| | - Joel Grebel
- Pritzker School of Molecular Engineering, University of Chicago, Chicago, Illinois 60637, USA
| | - Rhys G Povey
- Pritzker School of Molecular Engineering, University of Chicago, Chicago, Illinois 60637, USA
- Department of Physics, University of Chicago, Chicago, Illinois 60637, USA
| | - Andrew N Cleland
- Pritzker School of Molecular Engineering, University of Chicago, Chicago, Illinois 60637, USA
- Center for Molecular Engineering and Material Science Division, Argonne National Laboratory, Lemont, Illinois 60439, USA
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6
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Bhatt RP, Kilinc J, Höcker L, Jendrzejewski F. Stochastic dynamics of a few sodium atoms in presence of a cold potassium cloud. Sci Rep 2022; 12:2422. [PMID: 35165302 PMCID: PMC8844084 DOI: 10.1038/s41598-022-05778-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2021] [Accepted: 01/14/2022] [Indexed: 11/15/2022] Open
Abstract
Single particle resolution is a requirement for numerous experimental protocols that emulate the dynamics of small systems in a bath. Here, we accurately resolve through atom counting the stochastic dynamics of a few sodium atoms in presence of a cold potassium cloud. This capability enables us to rule out the effect of inter-species interaction on sodium atom number dynamics, at very low atomic densities present in these experiments. We study the noise sources for sodium and potassium in a common framework. Thereby, we assign the detection limits to 4.3 atoms for potassium and 0.2 atoms (corresponding to 96% fidelity) for sodium. This opens possibilities for future experiments with a few atoms immersed in a quantum degenerate gas.
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7
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Sadiek G, Al-Dress W, Shaglel S, Elhag H. Asymptotic Entanglement Sudden Death in Two Atoms with Dipole-Dipole and Ising Interactions Coupled to a Radiation Field at Non-Zero Detuning. ENTROPY 2021; 23:e23050629. [PMID: 34070139 PMCID: PMC8158345 DOI: 10.3390/e23050629] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/19/2021] [Revised: 05/11/2021] [Accepted: 05/13/2021] [Indexed: 11/22/2022]
Abstract
We investigate the time evolution and asymptotic behavior of a system of two two-level atoms (qubits) interacting off-resonance with a single mode radiation field. The two atoms are coupled to each other through dipole–dipole as well as Ising interactions. An exact analytic solution for the system dynamics that spans the entire phase space is provided. We focus on initial states that cause the system to evolve to entanglement sudden death (ESD) between the two atoms. We find that combining the Ising and dipole–dipole interactions is very powerful in controlling the entanglement dynamics and ESD compared with either one of them separately. Their effects on eliminating ESD may add up constructively or destructively depending on the type of Ising interaction (Ferromagnetic or anti-Ferromagnetic), the detuning parameter value, and the initial state of the system. The asymptotic behavior of the ESD is found to depend substantially on the initial state of the system, where ESD can be entirely eliminated by tuning the system parameters except in the case of an initial correlated Bell state. Interestingly, the entanglement, atomic population and quantum correlation between the two atoms and the field synchronize and reach asymptotically quasi-steady dynamic states. Each one of them ends up as a continuous irregular oscillation, where the collapse periods vanish, with a limited amplitude and an approximately constant mean value that depend on the initial state and the system parameters choice. This indicates an asymptotic continuous exchange of energy (and strong quantum correlation) between the atoms and the field takes place, accompanied by diminished ESD for these chosen setups of the system. This system can be realized in spin states of quantum dots or Rydberg atoms in optical cavities, and superconducting or hybrid qubits in linear resonators.
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Affiliation(s)
- Gehad Sadiek
- Department of Applied Physics and Astronomy, University of Sharjah, Sharjah 27272, United Arab Emirates
- Department of Physics, Ain Shams University, Cairo 11566, Egypt
- Correspondence:
| | - Wiam Al-Dress
- Department of Physics, Imam Muhammad Ibn Saud Islamic University, Riyadh 11432, Saudi Arabia;
| | - Salwa Shaglel
- Department of Physics, University of Siegen, 57068 Siegen, Germany;
| | - Hala Elhag
- Department of Physics, University of Hamburg, 22589 Hamburg, Germany;
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8
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Kothe G, Lukaschek M, Yago T, Link G, Ivanov KL, Lin TS. Initializing 2 14 Pure 14-Qubit Entangled Nuclear Spin States in a Hyperpolarized Molecular Solid. J Phys Chem Lett 2021; 12:3647-3654. [PMID: 33826347 DOI: 10.1021/acs.jpclett.1c00726] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Quantum entanglement has been realized on a variety of physical platforms such as quantum dots, trapped atomic ions, and superconductors. Here we introduce specific molecular solids as promising alternative platforms. Our model system is triplet pentacene in a host single crystal at level anticrossing (LAC) conditions. First, a laser pulse generates the triplet state and initiates entanglement between an electron spin and 14 hyperfine coupled proton spins (quantum bits or qubits). This gives rise to large nuclear spin polarization. Subsequently, a resonant high-power microwave (mw) pulse disentangles the electron spin from the nuclear spins. Simultaneously, high-dimensional multiqubit entanglement is formed among the proton spins. We verified the initialization of 214 pure 14-qubit entangled nuclear spin states with an average degree of entanglement of Eav = 0.77 ± 0.03. These results pave the way for large-scale quantum information processing with more than 10 000 multiqubit entangled states corresponding to computational (Hilbert) space dimensions of dim >1053.
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Affiliation(s)
- Gerd Kothe
- Department of Physical Chemistry, University of Freiburg, Albertstrasse 21, 79104 Freiburg, Germany
| | - Michail Lukaschek
- Department of Physical Chemistry, University of Freiburg, Albertstrasse 21, 79104 Freiburg, Germany
| | - Tomoaki Yago
- Department of Physical Chemistry, Graduate School of Science and Engineering, Saitama University, 255 Shimo-ohkubo, Sakura-ku, Saitama 338-8570, Japan
| | - Gerhard Link
- Department of Physical Chemistry, University of Freiburg, Albertstrasse 21, 79104 Freiburg, Germany
| | - Konstantin L Ivanov
- International Tomography Center, Siberian Branch of the Russian Academy of Science, Institutskaya 3a, Novosibirsk 630090, Russia
- Novosibirsk State University, Pirogova 2, Novosibirsk 630090, Russia
| | - Tien-Sung Lin
- Department of Chemistry, Washington University, One Brookings Drive, St. Louis, Missouri 63130, United States
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9
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Luo DW, Qian XF, Yu T. Nonlocal magnon entanglement generation in coupled hybrid cavity systems. OPTICS LETTERS 2021; 46:1073-1076. [PMID: 33649660 DOI: 10.1364/ol.414975] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/20/2020] [Accepted: 01/26/2021] [Indexed: 06/12/2023]
Abstract
We investigate dynamical generation of macroscopic nonlocal entanglements between two remote massive magnon-superconducting-circuit hybrid systems. Two fiber-coupled microwave cavities are employed to serve as an interaction channel connecting two sets of macroscopic hybrid units, each containing a magnon (hosted by an yttrium-iron-garnet sphere) and a superconducting-circuit qubit. Surprisingly, it is found that stronger coupling does not necessarily mean faster entanglement generation. The proposed hybrid system allows the existence of an optimal fiber coupling strength that requires the shortest amount of time to generate a systematic maximal entanglement. Our theoretical results are shown to be within the scope of specific parameters that can be achieved with current technology. The noise effects on the implementation of systems are also treated in a general environment, suggesting the robustness of entanglement generation. Our discrete-variable qubit-like entanglement theory of magnons may lead to direct applications in various quantum information tasks.
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10
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Zhong Y, Chang HS, Bienfait A, Dumur É, Chou MH, Conner CR, Grebel J, Povey RG, Yan H, Schuster DI, Cleland AN. Deterministic multi-qubit entanglement in a quantum network. Nature 2021; 590:571-575. [PMID: 33627810 DOI: 10.1038/s41586-021-03288-7] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2020] [Accepted: 12/15/2020] [Indexed: 01/31/2023]
Abstract
The generation of high-fidelity distributed multi-qubit entanglement is a challenging task for large-scale quantum communication and computational networks1-4. The deterministic entanglement of two remote qubits has recently been demonstrated with both photons5-10 and phonons11. However, the deterministic generation and transmission of multi-qubit entanglement has not been demonstrated, primarily owing to limited state-transfer fidelities. Here we report a quantum network comprising two superconducting quantum nodes connected by a one-metre-long superconducting coaxial cable, where each node includes three interconnected qubits. By directly connecting the cable to one qubit in each node, we transfer quantum states between the nodes with a process fidelity of 0.911 ± 0.008. We also prepare a three-qubit Greenberger-Horne-Zeilinger (GHZ) state12-14 in one node and deterministically transfer this state to the other node, with a transferred-state fidelity of 0.656 ± 0.014. We further use this system to deterministically generate a globally distributed two-node, six-qubit GHZ state with a state fidelity of 0.722 ± 0.021. The GHZ state fidelities are clearly above the threshold of 1/2 for genuine multipartite entanglement15, showing that this architecture can be used to coherently link together multiple superconducting quantum processors, providing a modular approach for building large-scale quantum computers16,17.
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Affiliation(s)
- Youpeng Zhong
- Pritzker School of Molecular Engineering, University of Chicago, Chicago, IL, USA.,Shenzhen Institute for Quantum Science and Engineering, Southern University of Science and Technology, Shenzhen, China
| | - Hung-Shen Chang
- Pritzker School of Molecular Engineering, University of Chicago, Chicago, IL, USA
| | - Audrey Bienfait
- Pritzker School of Molecular Engineering, University of Chicago, Chicago, IL, USA.,Université de Lyon, ENS de Lyon, Université Claude Bernard, CNRS, Laboratoire de Physique, Lyon, France
| | - Étienne Dumur
- Pritzker School of Molecular Engineering, University of Chicago, Chicago, IL, USA.,Institute for Molecular Engineering and Material Science Division, Argonne National Laboratory, Argonne, IL, USA.,Université Grenoble Alpes, CEA, INAC-Pheliqs, Grenoble, France
| | - Ming-Han Chou
- Pritzker School of Molecular Engineering, University of Chicago, Chicago, IL, USA.,Department of Physics, University of Chicago, Chicago, IL, USA
| | - Christopher R Conner
- Pritzker School of Molecular Engineering, University of Chicago, Chicago, IL, USA
| | - Joel Grebel
- Pritzker School of Molecular Engineering, University of Chicago, Chicago, IL, USA
| | - Rhys G Povey
- Pritzker School of Molecular Engineering, University of Chicago, Chicago, IL, USA.,Department of Physics, University of Chicago, Chicago, IL, USA
| | - Haoxiong Yan
- Pritzker School of Molecular Engineering, University of Chicago, Chicago, IL, USA
| | - David I Schuster
- Pritzker School of Molecular Engineering, University of Chicago, Chicago, IL, USA.,Department of Physics, University of Chicago, Chicago, IL, USA
| | - Andrew N Cleland
- Pritzker School of Molecular Engineering, University of Chicago, Chicago, IL, USA. .,Institute for Molecular Engineering and Material Science Division, Argonne National Laboratory, Argonne, IL, USA.
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11
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Chang HS, Zhong YP, Bienfait A, Chou MH, Conner CR, Dumur É, Grebel J, Peairs GA, Povey RG, Satzinger KJ, Cleland AN. Remote Entanglement via Adiabatic Passage Using a Tunably Dissipative Quantum Communication System. PHYSICAL REVIEW LETTERS 2020; 124:240502. [PMID: 32639797 DOI: 10.1103/physrevlett.124.240502] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/02/2020] [Accepted: 05/18/2020] [Indexed: 06/11/2023]
Abstract
Effective quantum communication between remote quantum nodes requires high fidelity quantum state transfer and remote entanglement generation. Recent experiments have demonstrated that microwave photons, as well as phonons, can be used to couple superconducting qubits, with a fidelity limited primarily by loss in the communication channel [P. Kurpiers et al., Nature (London) 558, 264 (2018)NATUAS0028-083610.1038/s41586-018-0195-y; C. J. Axline et al., Nat. Phys. 14, 705 (2018)NPAHAX1745-247310.1038/s41567-018-0115-y; P. Campagne-Ibarcq et al., Phys. Rev. Lett. 120, 200501 (2018)PRLTAO0031-900710.1103/PhysRevLett.120.200501; N. Leung et al., npj Quantum Inf. 5, 18 (2019)2056-638710.1038/s41534-019-0128-0; Y. P. Zhong et al., Nat. Phys. 15, 741 (2019)NPAHAX1745-247310.1038/s41567-019-0507-7; A. Bienfait et al., Science 364, 368 (2019)SCIEAS0036-807510.1126/science.aaw8415]. Adiabatic protocols can overcome channel loss by transferring quantum states without populating the lossy communication channel. Here, we present a unique superconducting quantum communication system, comprising two superconducting qubits connected by a 0.73 m-long communication channel. Significantly, we can introduce large tunable loss to the channel, allowing exploration of different entanglement protocols in the presence of dissipation. When set for minimum loss in the channel, we demonstrate an adiabatic quantum state transfer protocol that achieves 99% transfer efficiency as well as the deterministic generation of entangled Bell states with a fidelity of 96%, all without populating the intervening communication channel, and competitive with a qubit-resonant mode-qubit relay method. We also explore the performance of the adiabatic protocol in the presence of significant channel loss, and show that the adiabatic protocol protects against loss in the channel, achieving higher state transfer and entanglement fidelities than the relay method.
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Affiliation(s)
- H-S Chang
- Pritzker School of Molecular Engineering, University of Chicago, Chicago, Illinois 60637, USA
| | - Y P Zhong
- Pritzker School of Molecular Engineering, University of Chicago, Chicago, Illinois 60637, USA
| | - A Bienfait
- Pritzker School of Molecular Engineering, University of Chicago, Chicago, Illinois 60637, USA
| | - M-H Chou
- Pritzker School of Molecular Engineering, University of Chicago, Chicago, Illinois 60637, USA
- Department of Physics, University of Chicago, Chicago, Illinois 60637, USA
| | - C R Conner
- Pritzker School of Molecular Engineering, University of Chicago, Chicago, Illinois 60637, USA
| | - É Dumur
- Pritzker School of Molecular Engineering, University of Chicago, Chicago, Illinois 60637, USA
- Argonne National Laboratory, Argonne, Illinois 60439, USA
| | - J Grebel
- Pritzker School of Molecular Engineering, University of Chicago, Chicago, Illinois 60637, USA
| | - G A Peairs
- Pritzker School of Molecular Engineering, University of Chicago, Chicago, Illinois 60637, USA
- Department of Physics, University of California, Santa Barbara, California 93106, USA
| | - R G Povey
- Pritzker School of Molecular Engineering, University of Chicago, Chicago, Illinois 60637, USA
- Department of Physics, University of Chicago, Chicago, Illinois 60637, USA
| | - K J Satzinger
- Pritzker School of Molecular Engineering, University of Chicago, Chicago, Illinois 60637, USA
- Department of Physics, University of California, Santa Barbara, California 93106, USA
| | - A N Cleland
- Pritzker School of Molecular Engineering, University of Chicago, Chicago, Illinois 60637, USA
- Argonne National Laboratory, Argonne, Illinois 60439, USA
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12
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Sadiek G, Al-Drees W, Abdallah MS. Manipulating entanglement sudden death in two coupled two-level atoms interacting off-resonance with a radiation field: an exact treatment. OPTICS EXPRESS 2019; 27:33799-33825. [PMID: 31878441 DOI: 10.1364/oe.27.033799] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/10/2019] [Accepted: 10/27/2019] [Indexed: 06/10/2023]
Abstract
We study a model of two coupled two-level atoms (qubits) interacting off-resonance (at non-zero detuning) with a single mode radiation field. This system is of special interest in the field of quantum information processing (QIP) and can be realized in electron spin states in quantum dots or Rydberg atoms in optical cavities and superconducting qubits in linear resonators. We present an exact analytical solution for the time evolution of the system starting from any initial state. Utilizing this solution, we show how the entanglement sudden death (ESD), which represents a major threat to QIP, can be efficiently controlled by tuning atom-atom coupling and non-zero detuning. We demonstrate that while one of these two system parameters may not separately affect the ESD, combining the two can be very effective, as in the case of an initial correlated Bell state. However in other cases, such as a W-like initial state, they may have a competing impacts on ESD. Moreover, their combined effect can be used to create ESD in the system, as in the case of an anti-correlated initial Bell state. A clear synchronization between the population inversion collapse-revival pattern and the entanglement dynamics is observed at all system parameter combinations. Nevertheless, only for initial states that may evolve to ESD, the population inversion revival oscillations, where exchange of energy between the atoms and the field takes place, temporally coincide with the entanglement revival peaks, whereas the population collapse periods match the ESD intervals. The variation of the radiation field intensity has a clear impact on the duration of the ESD at any combination of the other system parameters.
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13
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Dogra S, Madhok V, Lakshminarayan A. Quantum signatures of chaos, thermalization, and tunneling in the exactly solvable few-body kicked top. Phys Rev E 2019; 99:062217. [PMID: 31330664 DOI: 10.1103/physreve.99.062217] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2018] [Indexed: 06/10/2023]
Abstract
Exactly solvable models that exhibit quantum signatures of classical chaos are both rare as well as important-more so in view of the fact that the mechanisms for ergodic behavior and thermalization in isolated quantum systems and its connections to nonintegrability are under active investigation. In this work, we study quantum systems of few qubits collectively modeled as a kicked top, a textbook example of quantum chaos. In particular, we show that the three- and four-qubit cases are exactly solvable and yet, interestingly, can display signatures of ergodicity and thermalization. Deriving analytical expressions for entanglement entropy and concurrence, we see agreement in certain parameter regimes between long-time average values and ensemble averages of random states with permutation symmetry. Comparing with results using the data of a recent transmons-based experiment realizing the three-qubit case, we find agreement for short times, including a peculiar steplike behavior in correlations of some states. In the case of four qubits we point to a precursor of dynamical tunneling between what in the classical limit would be two stable islands. Numerical results for larger number of qubits show the emergence of the classical limit including signatures of a bifurcation.
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Affiliation(s)
- Shruti Dogra
- Department of Physics, Indian Institute of Technology Madras, Chennai 600036, India
| | - Vaibhav Madhok
- Department of Physics, Indian Institute of Technology Madras, Chennai 600036, India
| | - Arul Lakshminarayan
- Department of Physics, Indian Institute of Technology Madras, Chennai 600036, India
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14
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Carollo F, Jack RL, Garrahan JP. Unraveling the Large Deviation Statistics of Markovian Open Quantum Systems. PHYSICAL REVIEW LETTERS 2019; 122:130605. [PMID: 31012635 DOI: 10.1103/physrevlett.122.130605] [Citation(s) in RCA: 38] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/03/2018] [Revised: 03/05/2019] [Indexed: 06/09/2023]
Abstract
We analyze dynamical large deviations of quantum trajectories in Markovian open quantum systems in their full generality. We derive a quantum level-2.5 large deviation principle for these systems, which describes the joint fluctuations of time-averaged quantum jump rates and of the time-averaged quantum state for long times. Like its level-2.5 counterpart for classical continuous-time Markov chains (which it contains as a special case), this description is both explicit and complete, as the statistics of arbitrary time-extensive dynamical observables can be obtained by contraction from the explicit level-2.5 rate functional we derive. Our approach uses an unraveled representation of the quantum dynamics which allows these statistics to be obtained by analyzing a classical stochastic process in the space of pure states. For quantum reset processes we show that the unraveled dynamics is semi-Markovian and derive bounds on the asymptotic variance of the number of quantum jumps which generalize classical thermodynamic uncertainty relations. We finish by discussing how our level-2.5 approach can be used to study large deviations of nonlinear functions of the state, such as measures of entanglement.
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Affiliation(s)
- Federico Carollo
- School of Physics and Astronomy and Centre for the Mathematics and Theoretical Physics of Quantum Non-Equilibrium Systems, University of Nottingham, Nottingham, NG7 2RD, United Kingdom
| | - Robert L Jack
- Department of Applied Mathematics and Theoretical Physics, University of Cambridge, Wilberforce Road, Cambridge CB3 0WA, United Kingdom and Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW, United Kingdom
| | - Juan P Garrahan
- School of Physics and Astronomy and Centre for the Mathematics and Theoretical Physics of Quantum Non-Equilibrium Systems, University of Nottingham, Nottingham, NG7 2RD, United Kingdom
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15
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Liu Y, Tian J, Betzholz R, Cai J. Pulsed Quantum-State Reconstruction of Dark Systems. PHYSICAL REVIEW LETTERS 2019; 122:110406. [PMID: 30951349 DOI: 10.1103/physrevlett.122.110406] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/29/2019] [Indexed: 06/09/2023]
Abstract
We propose a novel strategy to reconstruct the quantum state of dark systems, i.e., degrees of freedom that are not directly accessible for measurement or control. Our scheme relies on the quantum control of a two-level probe that exerts a state-dependent potential on the dark system. Using a sequence of control pulses applied to the probe makes it possible to tailor the information one can obtain and, for example, allows us to reconstruct the density operator of a dark spin as well as the Wigner characteristic function of a harmonic oscillator. Because of the symmetry of the applied pulse sequence, this scheme is robust against slow noise on the probe. The proof-of-principle experiments are readily feasible in solid-state spins and trapped ions.
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Affiliation(s)
- Yu Liu
- School of Physics, Huazhong University of Science and Technology, Wuhan 430074, China
- International Joint Laboratory on Quantum Sensing and Quantum Metrology, Huazhong University of Science and Technology, Wuhan 430074, China
| | - Jiazhao Tian
- School of Physics, Huazhong University of Science and Technology, Wuhan 430074, China
- International Joint Laboratory on Quantum Sensing and Quantum Metrology, Huazhong University of Science and Technology, Wuhan 430074, China
| | - Ralf Betzholz
- School of Physics, Huazhong University of Science and Technology, Wuhan 430074, China
- International Joint Laboratory on Quantum Sensing and Quantum Metrology, Huazhong University of Science and Technology, Wuhan 430074, China
| | - Jianming Cai
- School of Physics, Huazhong University of Science and Technology, Wuhan 430074, China
- International Joint Laboratory on Quantum Sensing and Quantum Metrology, Huazhong University of Science and Technology, Wuhan 430074, China
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16
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Gong M, Chen MC, Zheng Y, Wang S, Zha C, Deng H, Yan Z, Rong H, Wu Y, Li S, Chen F, Zhao Y, Liang F, Lin J, Xu Y, Guo C, Sun L, Castellano AD, Wang H, Peng C, Lu CY, Zhu X, Pan JW. Genuine 12-Qubit Entanglement on a Superconducting Quantum Processor. PHYSICAL REVIEW LETTERS 2019; 122:110501. [PMID: 30951346 DOI: 10.1103/physrevlett.122.110501] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/06/2018] [Indexed: 06/09/2023]
Abstract
We report the preparation and verification of a genuine 12-qubit entanglement in a superconducting processor. The processor that we designed and fabricated has qubits lying on a 1D chain with relaxation times ranging from 29.6 to 54.6 μs. The fidelity of the 12-qubit entanglement was measured to be above 0.5544±0.0025, exceeding the genuine multipartite entanglement threshold by 21 statistical standard deviations. After thermal cycling, the 12-qubit state fidelity was further improved to be above 0.707±0.008. Our entangling circuit to generate linear cluster states is depth invariant in the number of qubits and uses single- and double-qubit gates instead of collective interactions. Our results are a substantial step towards large-scale random circuit sampling and scalable measurement-based quantum computing.
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Affiliation(s)
- Ming Gong
- Hefei National Laboratory for Physical Sciences at Microscale and Department of Modern Physics, University of Science and Technology of China, Hefei, Anhui 230026, China
- Shanghai Branch, CAS Center for Excellence and Synergetic Innovation Center in Quantum Information and Quantum Physics, 10 University of Science and Technology of China, Shanghai 201315, China
| | - Ming-Cheng Chen
- Hefei National Laboratory for Physical Sciences at Microscale and Department of Modern Physics, University of Science and Technology of China, Hefei, Anhui 230026, China
- Shanghai Branch, CAS Center for Excellence and Synergetic Innovation Center in Quantum Information and Quantum Physics, 10 University of Science and Technology of China, Shanghai 201315, China
| | - Yarui Zheng
- Hefei National Laboratory for Physical Sciences at Microscale and Department of Modern Physics, University of Science and Technology of China, Hefei, Anhui 230026, China
- Shanghai Branch, CAS Center for Excellence and Synergetic Innovation Center in Quantum Information and Quantum Physics, 10 University of Science and Technology of China, Shanghai 201315, China
| | - Shiyu Wang
- Hefei National Laboratory for Physical Sciences at Microscale and Department of Modern Physics, University of Science and Technology of China, Hefei, Anhui 230026, China
- Shanghai Branch, CAS Center for Excellence and Synergetic Innovation Center in Quantum Information and Quantum Physics, 10 University of Science and Technology of China, Shanghai 201315, China
| | - Chen Zha
- Hefei National Laboratory for Physical Sciences at Microscale and Department of Modern Physics, University of Science and Technology of China, Hefei, Anhui 230026, China
- Shanghai Branch, CAS Center for Excellence and Synergetic Innovation Center in Quantum Information and Quantum Physics, 10 University of Science and Technology of China, Shanghai 201315, China
| | - Hui Deng
- Hefei National Laboratory for Physical Sciences at Microscale and Department of Modern Physics, University of Science and Technology of China, Hefei, Anhui 230026, China
- Shanghai Branch, CAS Center for Excellence and Synergetic Innovation Center in Quantum Information and Quantum Physics, 10 University of Science and Technology of China, Shanghai 201315, China
| | - Zhiguang Yan
- Hefei National Laboratory for Physical Sciences at Microscale and Department of Modern Physics, University of Science and Technology of China, Hefei, Anhui 230026, China
- Shanghai Branch, CAS Center for Excellence and Synergetic Innovation Center in Quantum Information and Quantum Physics, 10 University of Science and Technology of China, Shanghai 201315, China
| | - Hao Rong
- Hefei National Laboratory for Physical Sciences at Microscale and Department of Modern Physics, University of Science and Technology of China, Hefei, Anhui 230026, China
- Shanghai Branch, CAS Center for Excellence and Synergetic Innovation Center in Quantum Information and Quantum Physics, 10 University of Science and Technology of China, Shanghai 201315, China
| | - Yulin Wu
- Hefei National Laboratory for Physical Sciences at Microscale and Department of Modern Physics, University of Science and Technology of China, Hefei, Anhui 230026, China
- Shanghai Branch, CAS Center for Excellence and Synergetic Innovation Center in Quantum Information and Quantum Physics, 10 University of Science and Technology of China, Shanghai 201315, China
| | - Shaowei Li
- Hefei National Laboratory for Physical Sciences at Microscale and Department of Modern Physics, University of Science and Technology of China, Hefei, Anhui 230026, China
- Shanghai Branch, CAS Center for Excellence and Synergetic Innovation Center in Quantum Information and Quantum Physics, 10 University of Science and Technology of China, Shanghai 201315, China
| | - Fusheng Chen
- Hefei National Laboratory for Physical Sciences at Microscale and Department of Modern Physics, University of Science and Technology of China, Hefei, Anhui 230026, China
- Shanghai Branch, CAS Center for Excellence and Synergetic Innovation Center in Quantum Information and Quantum Physics, 10 University of Science and Technology of China, Shanghai 201315, China
| | - Youwei Zhao
- Hefei National Laboratory for Physical Sciences at Microscale and Department of Modern Physics, University of Science and Technology of China, Hefei, Anhui 230026, China
- Shanghai Branch, CAS Center for Excellence and Synergetic Innovation Center in Quantum Information and Quantum Physics, 10 University of Science and Technology of China, Shanghai 201315, China
| | - Futian Liang
- Hefei National Laboratory for Physical Sciences at Microscale and Department of Modern Physics, University of Science and Technology of China, Hefei, Anhui 230026, China
- Shanghai Branch, CAS Center for Excellence and Synergetic Innovation Center in Quantum Information and Quantum Physics, 10 University of Science and Technology of China, Shanghai 201315, China
| | - Jin Lin
- Hefei National Laboratory for Physical Sciences at Microscale and Department of Modern Physics, University of Science and Technology of China, Hefei, Anhui 230026, China
- Shanghai Branch, CAS Center for Excellence and Synergetic Innovation Center in Quantum Information and Quantum Physics, 10 University of Science and Technology of China, Shanghai 201315, China
| | - Yu Xu
- Hefei National Laboratory for Physical Sciences at Microscale and Department of Modern Physics, University of Science and Technology of China, Hefei, Anhui 230026, China
- Shanghai Branch, CAS Center for Excellence and Synergetic Innovation Center in Quantum Information and Quantum Physics, 10 University of Science and Technology of China, Shanghai 201315, China
| | - Cheng Guo
- Hefei National Laboratory for Physical Sciences at Microscale and Department of Modern Physics, University of Science and Technology of China, Hefei, Anhui 230026, China
- Shanghai Branch, CAS Center for Excellence and Synergetic Innovation Center in Quantum Information and Quantum Physics, 10 University of Science and Technology of China, Shanghai 201315, China
| | - Lihua Sun
- Hefei National Laboratory for Physical Sciences at Microscale and Department of Modern Physics, University of Science and Technology of China, Hefei, Anhui 230026, China
- Shanghai Branch, CAS Center for Excellence and Synergetic Innovation Center in Quantum Information and Quantum Physics, 10 University of Science and Technology of China, Shanghai 201315, China
| | - Anthony D Castellano
- Hefei National Laboratory for Physical Sciences at Microscale and Department of Modern Physics, University of Science and Technology of China, Hefei, Anhui 230026, China
- Shanghai Branch, CAS Center for Excellence and Synergetic Innovation Center in Quantum Information and Quantum Physics, 10 University of Science and Technology of China, Shanghai 201315, China
| | - Haohua Wang
- Department of Physics, Zhejiang University, Hangzhou, Zhejiang 310027, China
| | - Chengzhi Peng
- Hefei National Laboratory for Physical Sciences at Microscale and Department of Modern Physics, University of Science and Technology of China, Hefei, Anhui 230026, China
- Shanghai Branch, CAS Center for Excellence and Synergetic Innovation Center in Quantum Information and Quantum Physics, 10 University of Science and Technology of China, Shanghai 201315, China
| | - Chao-Yang Lu
- Hefei National Laboratory for Physical Sciences at Microscale and Department of Modern Physics, University of Science and Technology of China, Hefei, Anhui 230026, China
- Shanghai Branch, CAS Center for Excellence and Synergetic Innovation Center in Quantum Information and Quantum Physics, 10 University of Science and Technology of China, Shanghai 201315, China
| | - Xiaobo Zhu
- Hefei National Laboratory for Physical Sciences at Microscale and Department of Modern Physics, University of Science and Technology of China, Hefei, Anhui 230026, China
- Shanghai Branch, CAS Center for Excellence and Synergetic Innovation Center in Quantum Information and Quantum Physics, 10 University of Science and Technology of China, Shanghai 201315, China
| | - Jian-Wei Pan
- Hefei National Laboratory for Physical Sciences at Microscale and Department of Modern Physics, University of Science and Technology of China, Hefei, Anhui 230026, China
- Shanghai Branch, CAS Center for Excellence and Synergetic Innovation Center in Quantum Information and Quantum Physics, 10 University of Science and Technology of China, Shanghai 201315, China
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17
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Cardoso WB, Avelar AT, de Almeida NG, Colherinhas G. Robust Entanglement Generation in Lithium Ions Mediated by Graphene Quantum Dots Interaction. J Phys Chem A 2019; 123:1790-1795. [DOI: 10.1021/acs.jpca.8b11354] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Wesley B. Cardoso
- Instituto de Física, Universidade Federal de Goiás, 74690-900, Goiânia, Goiás, Brazil
| | - Ardiley T. Avelar
- Instituto de Física, Universidade Federal de Goiás, 74690-900, Goiânia, Goiás, Brazil
| | - Norton G. de Almeida
- Instituto de Física, Universidade Federal de Goiás, 74690-900, Goiânia, Goiás, Brazil
| | - Guilherme Colherinhas
- Instituto de Física, Universidade Federal de Goiás, 74690-900, Goiânia, Goiás, Brazil
- Departamento de Física, CEPAE, Universidade Federal de Goiás, 74690-900, Goiânia, Goiás, Brazil
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18
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Blair EP, Tóth G, Lent CS. Entanglement loss in molecular quantum-dot qubits due to interaction with the environment. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2018; 30:195602. [PMID: 29578454 DOI: 10.1088/1361-648x/aab98d] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
We study quantum entanglement loss due to environmental interaction in a condensed matter system with a complex geometry relevant to recent proposals for computing with single electrons at the nanoscale. We consider a system consisting of two qubits, each realized by an electron in a double quantum dot, which are initially in an entangled Bell state. The qubits are widely separated and each interacts with its own environment. The environment for each is modeled by surrounding double quantum dots placed at random positions with random orientations. We calculate the unitary evolution of the joint system and environment. The global state remains pure throughout. We examine the time dependence of the expectation value of the bipartite Clauser-Horne-Shimony-Holt (CHSH) and Brukner-Paunković-Rudolph-Vedral (BPRV) Bell operators and explore the emergence of correlations consistent with local realism. Though the details of this transition depend on the specific environmental geometry, we show how the results can be mapped on to a universal behavior with appropriate scaling. We determine the relevant disentanglement times based on realistic physical parameters for molecular double-dots.
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Affiliation(s)
- Enrique P Blair
- Electrical and Computer Engineering Department, Baylor University, Waco, TX, United States of America
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19
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Stabilized entanglement of massive mechanical oscillators. Nature 2018; 556:478-482. [DOI: 10.1038/s41586-018-0038-x] [Citation(s) in RCA: 299] [Impact Index Per Article: 49.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2017] [Accepted: 03/02/2018] [Indexed: 11/08/2022]
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20
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Reagor M, Osborn CB, Tezak N, Staley A, Prawiroatmodjo G, Scheer M, Alidoust N, Sete EA, Didier N, da Silva MP, Acala E, Angeles J, Bestwick A, Block M, Bloom B, Bradley A, Bui C, Caldwell S, Capelluto L, Chilcott R, Cordova J, Crossman G, Curtis M, Deshpande S, El Bouayadi T, Girshovich D, Hong S, Hudson A, Karalekas P, Kuang K, Lenihan M, Manenti R, Manning T, Marshall J, Mohan Y, O’Brien W, Otterbach J, Papageorge A, Paquette JP, Pelstring M, Polloreno A, Rawat V, Ryan CA, Renzas R, Rubin N, Russel D, Rust M, Scarabelli D, Selvanayagam M, Sinclair R, Smith R, Suska M, To TW, Vahidpour M, Vodrahalli N, Whyland T, Yadav K, Zeng W, Rigetti CT. Demonstration of universal parametric entangling gates on a multi-qubit lattice. SCIENCE ADVANCES 2018; 4:eaao3603. [PMID: 29423443 PMCID: PMC5804605 DOI: 10.1126/sciadv.aao3603] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/12/2017] [Accepted: 01/03/2018] [Indexed: 06/07/2023]
Abstract
We show that parametric coupling techniques can be used to generate selective entangling interactions for multi-qubit processors. By inducing coherent population exchange between adjacent qubits under frequency modulation, we implement a universal gate set for a linear array of four superconducting qubits. An average process fidelity of ℱ = 93% is estimated for three two-qubit gates via quantum process tomography. We establish the suitability of these techniques for computation by preparing a four-qubit maximally entangled state and comparing the estimated state fidelity with the expected performance of the individual entangling gates. In addition, we prepare an eight-qubit register in all possible bitstring permutations and monitor the fidelity of a two-qubit gate across one pair of these qubits. Across all these permutations, an average fidelity of ℱ = 91.6 ± 2.6% is observed. These results thus offer a path to a scalable architecture with high selectivity and low cross-talk.
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21
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Zajac DM, Sigillito AJ, Russ M, Borjans F, Taylor JM, Burkard G, Petta JR. Resonantly driven CNOT gate for electron spins. Science 2018; 359:439-442. [DOI: 10.1126/science.aao5965] [Citation(s) in RCA: 327] [Impact Index Per Article: 54.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2017] [Accepted: 11/28/2017] [Indexed: 01/25/2023]
Affiliation(s)
- D. M. Zajac
- Department of Physics, Princeton University, Princeton, NJ 08544, USA
| | - A. J. Sigillito
- Department of Physics, Princeton University, Princeton, NJ 08544, USA
| | - M. Russ
- Department of Physics, University of Konstanz, D-78457 Konstanz, Germany
| | - F. Borjans
- Department of Physics, Princeton University, Princeton, NJ 08544, USA
| | - J. M. Taylor
- Joint Quantum Institute and Joint Center for Quantum Information and Computer Science, NIST and University of Maryland, College Park, MD 20742, USA
- Research Center for Advanced Science and Technology, University of Tokyo, Tokyo, Japan
| | - G. Burkard
- Department of Physics, University of Konstanz, D-78457 Konstanz, Germany
| | - J. R. Petta
- Department of Physics, Princeton University, Princeton, NJ 08544, USA
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22
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Szańkowski P, Ramon G, Krzywda J, Kwiatkowski D, Cywiński Ł. Environmental noise spectroscopy with qubits subjected to dynamical decoupling. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2017; 29:333001. [PMID: 28569239 DOI: 10.1088/1361-648x/aa7648] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
A qubit subjected to pure dephasing due to classical Gaussian noise can be turned into a spectrometer of this noise by utilizing its readout under properly chosen dynamical decoupling (DD) sequences to reconstruct the power spectral density of the noise. We review the theory behind this DD-based noise spectroscopy technique, paying special attention to issues that arise when the environmental noise is non-Gaussian and/or it has truly quantum properties. While we focus on the theoretical basis of the method, we connect the discussed concepts with specific experiments, and provide an overview of environmental noise models relevant for solid-state based qubits, including quantum-dot based spin qubits, superconducting qubits, and NV centers in diamond.
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Affiliation(s)
- P Szańkowski
- Institute of Physics, Polish Academy of Sciences, Aleja Lotnikow 32/46, PL-02668 Warsaw, Poland
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23
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Welte S, Hacker B, Daiss S, Ritter S, Rempe G. Cavity Carving of Atomic Bell States. PHYSICAL REVIEW LETTERS 2017; 118:210503. [PMID: 28598645 DOI: 10.1103/physrevlett.118.210503] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/27/2017] [Indexed: 06/07/2023]
Abstract
We demonstrate entanglement generation of two neutral atoms trapped inside an optical cavity. Entanglement is created from initially separable two-atom states through carving with weak photon pulses reflected from the cavity. A polarization rotation of the photons heralds the entanglement. We show the successful implementation of two different protocols and the generation of all four Bell states with a maximum fidelity of (90±2)%. The protocol works for any distance between cavity-coupled atoms, and no individual addressing is required. Our result constitutes an important step towards applications in quantum networks, e.g., for entanglement swapping in a quantum repeater.
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Affiliation(s)
- Stephan Welte
- Max-Planck-Institut für Quantenoptik, Hans-Kopfermann-Strasse 1, 85748 Garching, Germany
| | - Bastian Hacker
- Max-Planck-Institut für Quantenoptik, Hans-Kopfermann-Strasse 1, 85748 Garching, Germany
| | - Severin Daiss
- Max-Planck-Institut für Quantenoptik, Hans-Kopfermann-Strasse 1, 85748 Garching, Germany
| | - Stephan Ritter
- Max-Planck-Institut für Quantenoptik, Hans-Kopfermann-Strasse 1, 85748 Garching, Germany
| | - Gerhard Rempe
- Max-Planck-Institut für Quantenoptik, Hans-Kopfermann-Strasse 1, 85748 Garching, Germany
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24
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Ballance CJ, Harty TP, Linke NM, Sepiol MA, Lucas DM. High-Fidelity Quantum Logic Gates Using Trapped-Ion Hyperfine Qubits. PHYSICAL REVIEW LETTERS 2016; 117:060504. [PMID: 27541450 DOI: 10.1103/physrevlett.117.060504] [Citation(s) in RCA: 117] [Impact Index Per Article: 14.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/30/2015] [Indexed: 05/02/2023]
Abstract
We demonstrate laser-driven two-qubit and single-qubit logic gates with respective fidelities 99.9(1)% and 99.9934(3)%, significantly above the ≈99% minimum threshold level required for fault-tolerant quantum computation, using qubits stored in hyperfine ground states of calcium-43 ions held in a room-temperature trap. We study the speed-fidelity trade-off for the two-qubit gate, for gate times between 3.8 μs and 520 μs, and develop a theoretical error model which is consistent with the data and which allows us to identify the principal technical sources of infidelity.
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Affiliation(s)
- C J Ballance
- Department of Physics, University of Oxford, Clarendon Laboratory, Parks Road, Oxford OX1 3PU, United Kingdom
| | - T P Harty
- Department of Physics, University of Oxford, Clarendon Laboratory, Parks Road, Oxford OX1 3PU, United Kingdom
| | - N M Linke
- Department of Physics, University of Oxford, Clarendon Laboratory, Parks Road, Oxford OX1 3PU, United Kingdom
| | - M A Sepiol
- Department of Physics, University of Oxford, Clarendon Laboratory, Parks Road, Oxford OX1 3PU, United Kingdom
| | - D M Lucas
- Department of Physics, University of Oxford, Clarendon Laboratory, Parks Road, Oxford OX1 3PU, United Kingdom
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25
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Kimchi-Schwartz ME, Martin L, Flurin E, Aron C, Kulkarni M, Tureci HE, Siddiqi I. Stabilizing Entanglement via Symmetry-Selective Bath Engineering in Superconducting Qubits. PHYSICAL REVIEW LETTERS 2016; 116:240503. [PMID: 27367372 DOI: 10.1103/physrevlett.116.240503] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/11/2015] [Indexed: 06/06/2023]
Abstract
Bath engineering, which utilizes coupling to lossy modes in a quantum system to generate nontrivial steady states, is a tantalizing alternative to gate- and measurement-based quantum science. Here, we demonstrate dissipative stabilization of entanglement between two superconducting transmon qubits in a symmetry-selective manner. We utilize the engineered symmetries of the dissipative environment to stabilize a target Bell state; we further demonstrate suppression of the Bell state of opposite symmetry due to parity selection rules. This implementation is resource efficient, achieves a steady-state fidelity F=0.70, and is scalable to multiple qubits.
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Affiliation(s)
- M E Kimchi-Schwartz
- Quantum Nanoelectronics Laboratory, Department of Physics, University of California, Berkeley, California 94720, USA
| | - L Martin
- Quantum Nanoelectronics Laboratory, Department of Physics, University of California, Berkeley, California 94720, USA
| | - E Flurin
- Quantum Nanoelectronics Laboratory, Department of Physics, University of California, Berkeley, California 94720, USA
| | - C Aron
- Department of Electrical Engineering, Princeton University, Princeton, New Jersey 08544, USA
- Laboratoire de Physique Théorique, École Normale Supérieure, CNRS, Paris, France
- Instituut voor Theoretische Fysica, KU Leuven, Belgium
| | - M Kulkarni
- Department of Physics, New York City College of Technology, The City University of New York, Brooklyn, New York 11201, USA
| | - H E Tureci
- Department of Electrical Engineering, Princeton University, Princeton, New Jersey 08544, USA
| | - I Siddiqi
- Quantum Nanoelectronics Laboratory, Department of Physics, University of California, Berkeley, California 94720, USA
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26
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Brange F, Malkoc O, Samuelsson P. Subdecoherence time generation and detection of orbital entanglement in quantum dots. PHYSICAL REVIEW LETTERS 2015; 114:176803. [PMID: 25978249 DOI: 10.1103/physrevlett.114.176803] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/16/2015] [Indexed: 06/04/2023]
Abstract
Recent experiments have demonstrated subdecoherence time control of individual single-electron orbital qubits. Here we propose a quantum-dot-based scheme for generation and detection of pairs of orbitally entangled electrons on a time scale much shorter than the decoherence time. The electrons are entangled, via two-particle interference, and transferred to the detectors during a single cotunneling event, making the scheme insensitive to charge noise. For sufficiently long detector dot lifetimes, cross-correlation detection of the dot charges can be performed with real-time counting techniques, providing for an unambiguous short-time Bell inequality test of orbital entanglement.
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Affiliation(s)
- F Brange
- Department of Physics, Lund University, Box 118, SE-221 00 Lund, Sweden
| | - O Malkoc
- Department of Physics, Lund University, Box 118, SE-221 00 Lund, Sweden
| | - P Samuelsson
- Department of Physics, Lund University, Box 118, SE-221 00 Lund, Sweden
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27
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Dong D, Chen C, Qi B, Petersen IR, Nori F. Robust manipulation of superconducting qubits in the presence of fluctuations. Sci Rep 2015; 5:7873. [PMID: 25598529 PMCID: PMC4297962 DOI: 10.1038/srep07873] [Citation(s) in RCA: 63] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2014] [Accepted: 12/12/2014] [Indexed: 11/09/2022] Open
Abstract
Superconducting quantum systems are promising candidates for quantum information processing due to their scalability and design flexibility. However, the existence of defects, fluctuations, and inaccuracies is unavoidable for practical superconducting quantum circuits. In this paper, a sampling-based learning control (SLC) method is used to guide the design of control fields for manipulating superconducting quantum systems. Numerical results for one-qubit systems and coupled two-qubit systems show that the "smart" fields learned using the SLC method can achieve robust manipulation of superconducting qubits, even in the presence of large fluctuations and inaccuracies.
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Affiliation(s)
- Daoyi Dong
- School of Engineering and Information Technology, University of New South Wales, Canberra 2600, Australia
| | - Chunlin Chen
- Department of Control and System Engineering, School of Management and Engineering, Nanjing University, Nanjing 210093, China
| | - Bo Qi
- Key Laboratory of Systems and Control, ISS, and National Center for Mathematics and Interdis-ciplinary Sciences, Academy of Mathematics and Systems Science, CAS, Beijing 100190, China
| | - Ian R Petersen
- School of Engineering and Information Technology, University of New South Wales, Canberra 2600, Australia
| | - Franco Nori
- 1] CEMS, RIKEN, Saitama351-0198, Japan [2] Physics Department, The University of Michigan, Ann Arbor, Michigan 48109-1040, USA
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28
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Felicetti S, Sanz M, Lamata L, Romero G, Johansson G, Delsing P, Solano E. Dynamical Casimir effect entangles artificial atoms. PHYSICAL REVIEW LETTERS 2014; 113:093602. [PMID: 25215982 DOI: 10.1103/physrevlett.113.093602] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/02/2014] [Indexed: 06/03/2023]
Abstract
We show that the physics underlying the dynamical Casimir effect may generate multipartite quantum correlations. To achieve it, we propose a circuit quantum electrodynamics scenario involving superconducting quantum interference devices, cavities, and superconducting qubits, also called artificial atoms. Our results predict the generation of highly entangled states for two and three superconducting qubits in different geometric configurations with realistic parameters. This proposal paves the way for a scalable method of multipartite entanglement generation in cavity networks through dynamical Casimir physics.
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Affiliation(s)
- S Felicetti
- Department of Physical Chemistry, University of the Basque Country UPV/EHU, Apartado 644, E-48080 Bilbao, Spain
| | - M Sanz
- Department of Physical Chemistry, University of the Basque Country UPV/EHU, Apartado 644, E-48080 Bilbao, Spain
| | - L Lamata
- Department of Physical Chemistry, University of the Basque Country UPV/EHU, Apartado 644, E-48080 Bilbao, Spain
| | - G Romero
- Department of Physical Chemistry, University of the Basque Country UPV/EHU, Apartado 644, E-48080 Bilbao, Spain
| | - G Johansson
- Department of Microtechnology and Nanoscience (MC2), Chalmers University of Technology, SE-412 96 Göteborg, Sweden
| | - P Delsing
- Department of Microtechnology and Nanoscience (MC2), Chalmers University of Technology, SE-412 96 Göteborg, Sweden
| | - E Solano
- Department of Physical Chemistry, University of the Basque Country UPV/EHU, Apartado 644, E-48080 Bilbao, Spain and IKERBASQUE, Basque Foundation for Science, Alameda Urquijo 36, 48011 Bilbao, Spain
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29
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Mezzacapo A, Lamata L, Filipp S, Solano E. Many-body interactions with tunable-coupling transmon qubits. PHYSICAL REVIEW LETTERS 2014; 113:050501. [PMID: 25126905 DOI: 10.1103/physrevlett.113.050501] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/21/2014] [Indexed: 06/03/2023]
Abstract
The efficient implementation of many-body interactions in superconducting circuits allows for the realization of multipartite entanglement and topological codes, as well as the efficient simulation of highly correlated fermionic systems. We propose the engineering of fast multiqubit interactions with tunable transmon-resonator couplings. This dynamics is obtained by the modulation of magnetic fluxes threading superconducting quantum interference device loops embedded in the transmon devices. We consider the feasibility of the proposed implementation in a realistic scenario and discuss potential applications.
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Affiliation(s)
- A Mezzacapo
- Department of Physical Chemistry, University of the Basque Country UPV/EHU, Apartado 644, E-48080 Bilbao, Spain
| | - L Lamata
- Department of Physical Chemistry, University of the Basque Country UPV/EHU, Apartado 644, E-48080 Bilbao, Spain
| | - S Filipp
- Department of Physics, ETH Zürich, CH-8093 Zürich, Switzerland
| | - E Solano
- Department of Physical Chemistry, University of the Basque Country UPV/EHU, Apartado 644, E-48080 Bilbao, Spain and IKERBASQUE, Basque Foundation for Science, Alameda Urquijo 36, 48011 Bilbao, Spain
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30
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Encoding a qubit with Majorana modes in superconducting circuits. Sci Rep 2014; 4:5535. [PMID: 24985708 PMCID: PMC4078313 DOI: 10.1038/srep05535] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2013] [Accepted: 06/16/2014] [Indexed: 11/08/2022] Open
Abstract
Majorana fermions are long-sought exotic particles that are their own antiparticles. Here we propose to utilize superconducting circuits to construct two superconducting-qubit arrays where Majorana modes can occur. A so-called Majorana qubit is encoded by using the unpaired Majorana modes, which emerge at the left and right ends of the chain in the Majorana-fermion representation. We also show this Majorana qubit in the spin representation and its advantage, over a single superconducting qubit, regarding quantum coherence. Moreover, we propose to use four superconducting qubits as the smallest system to demonstrate the braiding of Majorana modes and show how the states before and after braiding Majoranas can be discriminated.
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31
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Roch N, Schwartz ME, Motzoi F, Macklin C, Vijay R, Eddins AW, Korotkov AN, Whaley KB, Sarovar M, Siddiqi I. Observation of measurement-induced entanglement and quantum trajectories of remote superconducting qubits. PHYSICAL REVIEW LETTERS 2014; 112:170501. [PMID: 24836225 DOI: 10.1103/physrevlett.112.170501] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/08/2014] [Indexed: 05/23/2023]
Abstract
The creation of a quantum network requires the distribution of coherent information across macroscopic distances. We demonstrate the entanglement of two superconducting qubits, separated by more than a meter of coaxial cable, by designing a joint measurement that probabilistically projects onto an entangled state. By using a continuous measurement scheme, we are further able to observe single quantum trajectories of the joint two-qubit state, confirming the validity of the quantum Bayesian formalism for a cascaded system. Our results allow us to resolve the dynamics of continuous projection onto the entangled manifold, in quantitative agreement with theory.
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Affiliation(s)
- N Roch
- Quantum Nanoelectronics Laboratory, Department of Physics, University of California, Berkeley, California 94720, USA
| | - M E Schwartz
- Quantum Nanoelectronics Laboratory, Department of Physics, University of California, Berkeley, California 94720, USA
| | - F Motzoi
- Department of Chemistry, University of California, Berkeley, California 94720, USA
| | - C Macklin
- Quantum Nanoelectronics Laboratory, Department of Physics, University of California, Berkeley, California 94720, USA
| | - R Vijay
- Department of Condensed Matter Physics and Materials Science, Tata Institute of Fundamental Research, Mumbai 400005, India
| | - A W Eddins
- Quantum Nanoelectronics Laboratory, Department of Physics, University of California, Berkeley, California 94720, USA
| | - A N Korotkov
- Department of Electrical Engineering, University of California, Riverside, California 92521, USA
| | - K B Whaley
- Department of Chemistry, University of California, Berkeley, California 94720, USA
| | - M Sarovar
- Scalable and Secure Systems Research (08961), Sandia National Laboratories, Livermore, California 94550, USA
| | - I Siddiqi
- Quantum Nanoelectronics Laboratory, Department of Physics, University of California, Berkeley, California 94720, USA
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32
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Saira OP, Groen JP, Cramer J, Meretska M, de Lange G, DiCarlo L. Entanglement genesis by ancilla-based parity measurement in 2D circuit QED. PHYSICAL REVIEW LETTERS 2014; 112:070502. [PMID: 24579578 DOI: 10.1103/physrevlett.112.070502] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/22/2013] [Indexed: 06/03/2023]
Abstract
We present an indirect two-qubit parity meter in planar circuit quantum electrodynamics, realized by discrete interaction with an ancilla and a subsequent projective ancilla measurement with a dedicated, dispersively coupled resonator. Quantum process tomography and successful entanglement by measurement demonstrate that the meter is intrinsically quantum nondemolition. Separate interaction and measurement steps allow the execution of subsequent data-qubit operations in parallel with ancilla measurement, offering time savings over continuous schemes.
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Affiliation(s)
- O-P Saira
- Kavli Institute of Nanoscience, Delft University of Technology, Post Office Box 5046, 2600 GA Delft, The Netherlands
| | - J P Groen
- Kavli Institute of Nanoscience, Delft University of Technology, Post Office Box 5046, 2600 GA Delft, The Netherlands
| | - J Cramer
- Kavli Institute of Nanoscience, Delft University of Technology, Post Office Box 5046, 2600 GA Delft, The Netherlands
| | - M Meretska
- Kavli Institute of Nanoscience, Delft University of Technology, Post Office Box 5046, 2600 GA Delft, The Netherlands
| | - G de Lange
- Kavli Institute of Nanoscience, Delft University of Technology, Post Office Box 5046, 2600 GA Delft, The Netherlands
| | - L DiCarlo
- Kavli Institute of Nanoscience, Delft University of Technology, Post Office Box 5046, 2600 GA Delft, The Netherlands
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33
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Tan X, Zhang DW, Zhang Z, Yu Y, Han S, Zhu SL. Demonstration of geometric Landau-Zener interferometry in a superconducting qubit. PHYSICAL REVIEW LETTERS 2014; 112:027001. [PMID: 24484040 DOI: 10.1103/physrevlett.112.027001] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/04/2013] [Indexed: 06/03/2023]
Abstract
Geometric quantum manipulation and Landau-Zener interferometry have been separately explored in many quantum systems. In this Letter, we combine these two approaches to study the dynamics of a superconducting phase qubit. We experimentally demonstrate Landau-Zener interferometry based on the pure geometric phases in this solid-state qubit. We observe the interference caused by a pure geometric phase accumulated in the evolution between two consecutive Landau-Zener transitions, while the dynamical phase is canceled out by a spin-echo pulse. The full controllability of the qubit state as a function of the intrinsically robust geometric phase provides a promising approach for quantum state manipulation.
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Affiliation(s)
- Xinsheng Tan
- National Laboratory of Solid State Microstructures, School of Physics, Nanjing University, Nanjing 210093, China and Department of Physics and Astronomy, University of Kansas, Lawrence, Kansas 66045, USA
| | - Dan-Wei Zhang
- Laboratory of Quantum Engineering and Quantum Materials, SPTE, South China Normal University, Guangzhou 510006, China
| | - Zhentao Zhang
- National Laboratory of Solid State Microstructures, School of Physics, Nanjing University, Nanjing 210093, China
| | - Yang Yu
- National Laboratory of Solid State Microstructures, School of Physics, Nanjing University, Nanjing 210093, China
| | - Siyuan Han
- Department of Physics and Astronomy, University of Kansas, Lawrence, Kansas 66045, USA
| | - Shi-Liang Zhu
- National Laboratory of Solid State Microstructures, School of Physics, Nanjing University, Nanjing 210093, China and Laboratory of Quantum Engineering and Quantum Materials, SPTE, South China Normal University, Guangzhou 510006, China
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34
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Steffen L, Salathe Y, Oppliger M, Kurpiers P, Baur M, Lang C, Eichler C, Puebla-Hellmann G, Fedorov A, Wallraff A. Deterministic quantum teleportation with feed-forward in a solid state system. Nature 2013; 500:319-22. [PMID: 23955231 DOI: 10.1038/nature12422] [Citation(s) in RCA: 58] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2013] [Accepted: 06/28/2013] [Indexed: 11/09/2022]
Abstract
Engineered macroscopic quantum systems based on superconducting electronic circuits are attractive for experimentally exploring diverse questions in quantum information science. At the current state of the art, quantum bits (qubits) are fabricated, initialized, controlled, read out and coupled to each other in simple circuits. This enables the realization of basic logic gates, the creation of complex entangled states and the demonstration of algorithms or error correction. Using different variants of low-noise parametric amplifiers, dispersive quantum non-demolition single-shot readout of single-qubit states with high fidelity has enabled continuous and discrete feedback control of single qubits. Here we realize full deterministic quantum teleportation with feed-forward in a chip-based superconducting circuit architecture. We use a set of two parametric amplifiers for both joint two-qubit and individual qubit single-shot readout, combined with flexible real-time digital electronics. Our device uses a crossed quantum bus technology that allows us to create complex networks with arbitrary connecting topology in a planar architecture. The deterministic teleportation process succeeds with order unit probability for any input state, as we prepare maximally entangled two-qubit states as a resource and distinguish all Bell states in a single two-qubit measurement with high efficiency and high fidelity. We teleport quantum states between two macroscopic systems separated by 6 mm at a rate of 10(4) s(-1), exceeding other reported implementations. The low transmission loss of superconducting waveguides is likely to enable the range of this and other schemes to be extended to significantly larger distances, enabling tests of non-locality and the realization of elements for quantum communication at microwave frequencies. The demonstrated feed-forward may also find application in error correction schemes.
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Affiliation(s)
- L Steffen
- Department of Physics, ETH Zurich, CH-8093 Zurich, Switzerland.
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35
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Sauer S, Gneiting C, Buchleitner A. Optimal coherent control to counteract dissipation. PHYSICAL REVIEW LETTERS 2013; 111:030405. [PMID: 23909299 DOI: 10.1103/physrevlett.111.030405] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/19/2013] [Indexed: 06/02/2023]
Abstract
We study to what extent the detrimental impact of dissipation on quantum properties can be compensated by suitable coherent dynamics. To this end, we develop a general method to determine the control Hamiltonian that optimally counteracts a given dissipation mechanism, in order to sustain the desired property, and apply it to two exemplary target properties: the coherence of a decaying two-level system and the entanglement of two qubits in the presence of local dissipation.
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Affiliation(s)
- Simeon Sauer
- Physikalisches Institut, Albert-Ludwigs-Universität Freiburg, Hermann-Herder-Strasse 3, D-79104 Freiburg, Germany
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36
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Shalibo Y, Resh R, Fogel O, Shwa D, Bialczak R, Martinis JM, Katz N. Direct Wigner tomography of a superconducting anharmonic oscillator. PHYSICAL REVIEW LETTERS 2013; 110:100404. [PMID: 23521235 DOI: 10.1103/physrevlett.110.100404] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/12/2012] [Revised: 01/06/2013] [Indexed: 06/01/2023]
Abstract
The analysis of wave-packet dynamics may be greatly simplified when viewed in phase space. While harmonic oscillators are often used as a convenient platform to study wave packets, arbitrary state preparation in these systems is more challenging. Here, we demonstrate a direct measurement of the Wigner distribution of complex photon states in an anharmonic oscillator--a superconducting phase circuit, biased in the small anharmonicity regime. We apply our method on nondispersive wave packets to explicitly show phase locking in states prepared by a frequency chirp. This method requires a simple calibration, and is easily applicable in our system out to the fifth level.
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Affiliation(s)
- Yoni Shalibo
- Racah Institute of Physics, The Hebrew University of Jerusalem, Jerusalem 91904, Israel
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37
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Liu S, Li J, Yu R, Wu Y. Achieving maximum entanglement between two nitrogen-vacancy centers coupling to a whispering-gallery-mode microresonator. OPTICS EXPRESS 2013; 21:3501-3515. [PMID: 23481808 DOI: 10.1364/oe.21.003501] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
We investigate the entanglement generation between two nitrogen-vacancy (NV) centers in diamond nanocrystal coupled to a high-Q counterpropagating twin whispering-gallery modes (WGMs) of a microtoroidal resonator. For looking into the degree and dynamics of the entanglement, we calculate the concurrence using the microscopic master equation approach. The influences of the coupling strength between the WGMs (or the size of the two spherical NV centers), the distance between two NV centers, the frequency detuning between the NV center and microresonator, and the initial state of the system on the dynamics of concurrence are discussed in detail. It is found that the maximum entanglement between the two NV centers can be created by properly adjusting these controllable system parameters. Our results may provide further insight into future solid-state cavity quantum electrodynamics (CQED) system for quantum information engineering.
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Affiliation(s)
- Siping Liu
- Wuhan National Laboratory for Optoelectronics and School of Physics, Huazhong University of Science and Technology, Wuhan 430074, China
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38
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Alicki R, Miklaszewski W. Strong-coupling BCS models of Josephson qubits. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2013; 25:035701. [PMID: 23221260 DOI: 10.1088/0953-8984/25/3/035701] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
The strong-coupling version of the BCS theory for superconductors is used to derive microscopic models for all types of small Josephson junctions--charge qubit, flux qubit and phase qubit. Applied to Josephson qubits it yields a more complicated structure of the lowest-lying energy levels than that obtained from phenomenological models based on quantization of the Kirchhoff equations. In particular, highly degenerate levels emerge, which act as probability sinks for the qubit. The alternative formulae concerning spectra of superconducting qubits are presented and compared with the experimental data. In contrast to the existing theories those formulae contain microscopic parameters of the model. In particular, for the first time, the density of Cooper pairs at zero temperature is estimated for an Al-based flux qubit. Finally, the question whether small Josephson junctions can be treated as macroscopic quantum systems is briefly discussed.
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Affiliation(s)
- R Alicki
- Institute of Theoretical Physics and Astrophysics, University of Gdańsk, Wita Stwosza 57, PL 80-952 Gdańsk, Poland
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39
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Poletto S, Gambetta JM, Merkel ST, Smolin JA, Chow JM, Córcoles AD, Keefe GA, Rothwell MB, Rozen JR, Abraham DW, Rigetti C, Steffen M. Entanglement of two superconducting qubits in a waveguide cavity via monochromatic two-photon excitation. PHYSICAL REVIEW LETTERS 2012; 109:240505. [PMID: 23368296 DOI: 10.1103/physrevlett.109.240505] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/13/2012] [Indexed: 06/01/2023]
Abstract
We report a system where fixed interactions between noncomputational levels make bright the otherwise forbidden two-photon |00}→|11} transition. The system is formed by hand selection and assembly of two discrete component transmon-style superconducting qubits inside a rectangular microwave cavity. The application of a monochromatic drive tuned to this transition induces two-photon Rabi-like oscillations between the ground and doubly excited states via the Bell basis. The system therefore allows all-microwave two-qubit universal control with the same techniques and hardware required for single qubit control. We report Ramsey-like and spin echo sequences with the generated Bell states, and measure a two-qubit gate fidelity of F(g)=90% (unconstrained) and 86% (maximum likelihood estimator).
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Affiliation(s)
- S Poletto
- IBM TJ Watson Research Center, Yorktown Heights, New York 10598, USA
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40
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Sabín C, Peropadre B, del Rey M, Martín-Martínez E. Extracting past-future vacuum correlations using circuit QED. PHYSICAL REVIEW LETTERS 2012; 109:033602. [PMID: 22861847 DOI: 10.1103/physrevlett.109.033602] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/15/2012] [Revised: 05/25/2012] [Indexed: 06/01/2023]
Abstract
We propose a realistic circuit QED experiment to test the extraction of past-future vacuum entanglement to a pair of superconducting qubits. The qubit P interacts with the quantum field along an open transmission line for an interval T(on) and then, after a time-lapse T(off), the qubit F starts interacting for a time T(on) in a symmetric fashion. After that, past-future quantum correlations will have transferred to the qubits, even if the qubits do not coexist at the same time. We show that this experiment can be realized with current technology and discuss its utility as a possible implementation of a quantum memory.
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Affiliation(s)
- Carlos Sabín
- Instituto de Física Fundamental, CSIC, Serrano 113-B, 28006 Madrid, Spain.
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41
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Gustavsson S, Yan F, Bylander J, Yoshihara F, Nakamura Y, Orlando TP, Oliver WD. Dynamical decoupling and dephasing in interacting two-level systems. PHYSICAL REVIEW LETTERS 2012; 109:010502. [PMID: 23031094 DOI: 10.1103/physrevlett.109.010502] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/25/2012] [Indexed: 06/01/2023]
Abstract
We implement dynamical decoupling techniques to mitigate noise and enhance the lifetime of an entangled state that is formed in a superconducting flux qubit coupled to a microscopic two-level system. By rapidly changing the qubit's transition frequency relative to the two-level system, we realize a refocusing pulse that reduces dephasing due to fluctuations in the transition frequencies, thereby improving the coherence time of the entangled state. The coupling coherence is further enhanced when applying multiple refocusing pulses, in agreement with our 1/f noise model. The results are applicable to any two-qubit system with transverse coupling and they highlight the potential of decoupling techniques for improving two-qubit gate fidelities, an essential prerequisite for implementing fault-tolerant quantum computing.
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Affiliation(s)
- Simon Gustavsson
- Research Laboratory of Electronics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
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42
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Chow JM, Córcoles AD, Gambetta JM, Rigetti C, Johnson BR, Smolin JA, Rozen JR, Keefe GA, Rothwell MB, Ketchen MB, Steffen M. Simple all-microwave entangling gate for fixed-frequency superconducting qubits. PHYSICAL REVIEW LETTERS 2011; 107:080502. [PMID: 21929152 DOI: 10.1103/physrevlett.107.080502] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/02/2011] [Indexed: 05/31/2023]
Abstract
We demonstrate an all-microwave two-qubit gate on superconducting qubits which are fixed in frequency at optimal bias points. The gate requires no additional subcircuitry and is tunable via the amplitude of microwave irradiation on one qubit at the transition frequency of the other. We use the gate to generate entangled states with a maximal extracted concurrence of 0.88, and quantum process tomography reveals a gate fidelity of 81%.
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Affiliation(s)
- Jerry M Chow
- IBM T. J. Watson Research Center, Yorktown Heights, New York 10598, USA
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43
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Zhou XQ, Ralph TC, Kalasuwan P, Zhang M, Peruzzo A, Lanyon BP, O'Brien JL. Adding control to arbitrary unknown quantum operations. Nat Commun 2011; 2:413. [PMID: 21811242 PMCID: PMC3267055 DOI: 10.1038/ncomms1392] [Citation(s) in RCA: 87] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2010] [Accepted: 06/15/2011] [Indexed: 11/18/2022] Open
Abstract
Although quantum computers promise significant advantages, the complexity of quantum algorithms remains a major technological obstacle. We have developed and demonstrated an architecture-independent technique that simplifies adding control qubits to arbitrary quantum operations—a requirement in many quantum algorithms, simulations and metrology. The technique, which is independent of how the operation is done, does not require knowledge of what the operation is, and largely separates the problems of how to implement a quantum operation in the laboratory and how to add a control. Here, we demonstrate an entanglement-based version in a photonic system, realizing a range of different two-qubit gates with high fidelity. Quantum computing has advantages over conventional computing, but the complexity of quantum algorithms creates technological challenges. Here, an architecture-independent technique, that simplifies adding control qubits to arbitrary quantum operations, is developed and demonstrated.
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Affiliation(s)
- Xiao-Qi Zhou
- Centre for Quantum Photonics, H.H. Wills Physics Laboratory & Department of Electrical and Electronic Engineering, University of Bristol, UK
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44
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45
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Bialczak RC, Ansmann M, Hofheinz M, Lenander M, Lucero E, Neeley M, O'Connell AD, Sank D, Wang H, Weides M, Wenner J, Yamamoto T, Cleland AN, Martinis JM. Fast tunable coupler for superconducting qubits. PHYSICAL REVIEW LETTERS 2011; 106:060501. [PMID: 21405448 DOI: 10.1103/physrevlett.106.060501] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/15/2010] [Indexed: 05/30/2023]
Abstract
A major challenge in the field of quantum computing is the construction of scalable qubit coupling architectures. Here, we demonstrate a novel tunable coupling circuit that allows superconducting qubits to be coupled over long distances. We show that the interqubit coupling strength can be arbitrarily tuned over nanosecond time scales within a sequence that mimics actual use in an algorithm. The coupler has a measured on/off ratio of 1000. The design is self-contained and physically separate from the qubits, allowing the coupler to be used as a module to connect a variety of elements such as qubits, resonators, amplifiers, and readout circuitry over distances much larger than nearest-neighbor. Such design flexibility is likely to be useful for a scalable quantum computer.
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Affiliation(s)
- R C Bialczak
- Department of Physics, University of California, Santa Barbara, California 93106, USA
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46
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Gambetta JM, Houck AA, Blais A. Superconducting qubit with Purcell protection and tunable coupling. PHYSICAL REVIEW LETTERS 2011; 106:030502. [PMID: 21405262 DOI: 10.1103/physrevlett.106.030502] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/21/2010] [Indexed: 05/30/2023]
Abstract
We present a superconducting qubit for the circuit quantum electrodynamics architecture that has a tunable qubit-resonator coupling strength g. This coupling can be tuned from zero to values that are comparable with other superconducting qubits. At g = 0, the qubit is in a decoherence-free subspace with respect to spontaneous emission induced by the Purcell effect. Furthermore, we show that in this decoherence-free subspace, the state of the qubit can still be measured by either a dispersive shift on the resonance frequency of the resonator or by a cycling-type measurement.
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Affiliation(s)
- J M Gambetta
- Department of Applied Mathematics, Institute for Quantum Computing, University of Waterloo, Waterloo, Ontario, Canada N2L 3G1
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47
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Choi KS, Goban A, Papp SB, van Enk SJ, Kimble HJ. Entanglement of spin waves among four quantum memories. Nature 2010; 468:412-6. [DOI: 10.1038/nature09568] [Citation(s) in RCA: 100] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2010] [Accepted: 10/05/2010] [Indexed: 11/09/2022]
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Dicarlo L, Reed MD, Sun L, Johnson BR, Chow JM, Gambetta JM, Frunzio L, Girvin SM, Devoret MH, Schoelkopf RJ. Preparation and measurement of three-qubit entanglement in a superconducting circuit. Nature 2010; 467:574-8. [PMID: 20882013 DOI: 10.1038/nature09416] [Citation(s) in RCA: 443] [Impact Index Per Article: 31.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2010] [Accepted: 08/09/2010] [Indexed: 11/09/2022]
Abstract
Traditionally, quantum entanglement has been central to foundational discussions of quantum mechanics. The measurement of correlations between entangled particles can have results at odds with classical behaviour. These discrepancies grow exponentially with the number of entangled particles. With the ample experimental confirmation of quantum mechanical predictions, entanglement has evolved from a philosophical conundrum into a key resource for technologies such as quantum communication and computation. Although entanglement in superconducting circuits has been limited so far to two qubits, the extension of entanglement to three, eight and ten qubits has been achieved among spins, ions and photons, respectively. A key question for solid-state quantum information processing is whether an engineered system could display the multi-qubit entanglement necessary for quantum error correction, which starts with tripartite entanglement. Here, using a circuit quantum electrodynamics architecture, we demonstrate deterministic production of three-qubit Greenberger-Horne-Zeilinger (GHZ) states with fidelity of 88 per cent, measured with quantum state tomography. Several entanglement witnesses detect genuine three-qubit entanglement by violating biseparable bounds by 830 ± 80 per cent. We demonstrate the first step of basic quantum error correction, namely the encoding of a logical qubit into a manifold of GHZ-like states using a repetition code. The integration of this encoding with decoding and error-correcting steps in a feedback loop will be the next step for quantum computing with integrated circuits.
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Affiliation(s)
- L Dicarlo
- Department of Physics, Yale University, New Haven, Connecticut 06511, USA.
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Neeley M, Bialczak RC, Lenander M, Lucero E, Mariantoni M, O'Connell AD, Sank D, Wang H, Weides M, Wenner J, Yin Y, Yamamoto T, Cleland AN, Martinis JM. Generation of three-qubit entangled states using superconducting phase qubits. Nature 2010; 467:570-3. [PMID: 20882012 DOI: 10.1038/nature09418] [Citation(s) in RCA: 311] [Impact Index Per Article: 22.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2010] [Accepted: 08/11/2010] [Indexed: 11/09/2022]
Abstract
Entanglement is one of the key resources required for quantum computation, so the experimental creation and measurement of entangled states is of crucial importance for various physical implementations of quantum computers. In superconducting devices, two-qubit entangled states have been demonstrated and used to show violations of Bell's inequality and to implement simple quantum algorithms. Unlike the two-qubit case, where all maximally entangled two-qubit states are equivalent up to local changes of basis, three qubits can be entangled in two fundamentally different ways. These are typified by the states |GHZ>= (|000+ |111>)/ sqrt [2] and |W>= (|001> + |010> + |100>)/ sqrt [3]. Here we demonstrate the operation of three coupled superconducting phase qubits and use them to create and measure |GHZ> and |W>states. The states are fully characterized using quantum state tomography and are shown to satisfy entanglement witnesses, confirming that they are indeed examples of three-qubit entanglement and are not separable into mixtures of two-qubit entanglement.
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Affiliation(s)
- Matthew Neeley
- Department of Physics, University of California, Santa Barbara, California 93106, USA
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Steffen M, Kumar S, Divincenzo DP, Rozen JR, Keefe GA, Rothwell MB, Ketchen MB. High-coherence hybrid superconducting qubit. PHYSICAL REVIEW LETTERS 2010; 105:100502. [PMID: 20867498 DOI: 10.1103/physrevlett.105.100502] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/30/2010] [Indexed: 05/27/2023]
Abstract
We report quantum coherence measurements of a superconducting qubit whose design is a hybrid of several existing types. Excellent coherence times are found: T2∼T1∼1.5 μs. The topology of the qubit is that of a traditional three-junction flux qubit, but it has a large shunting capacitance, and the ratio of the junction critical currents is chosen so that the qubit potential has a single-well form. The qubit has a sizable nonlinearity, but its sign is reversed compared with most other popular qubit designs. The qubit is read out dispersively using a high-Q resonator in a λ/2 configuration.
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Affiliation(s)
- Matthias Steffen
- IBM Watson Research Center, Yorktown Heights, New York 10598, USA
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