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Lecocq F, Ranzani L, Peterson GA, Cicak K, Jin XY, Simmonds RW, Teufel JD, Aumentado J. Efficient Qubit Measurement with a Nonreciprocal Microwave Amplifier. Phys Rev Lett 2021; 126:020502. [PMID: 33512236 DOI: 10.1103/physrevlett.126.020502] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/01/2020] [Accepted: 12/07/2020] [Indexed: 06/12/2023]
Abstract
The act of observing a quantum object fundamentally perturbs its state, resulting in a random walk toward an eigenstate of the measurement operator. Ideally, the measurement is responsible for all dephasing of the quantum state. In practice, imperfections in the measurement apparatus limit or corrupt the flow of information required for quantum feedback protocols, an effect quantified by the measurement efficiency. Here, we demonstrate the efficient measurement of a superconducting qubit using a nonreciprocal parametric amplifier to directly monitor the microwave field of a readout cavity. By mitigating the losses between the cavity and the amplifier, we achieve a measurement efficiency of (72±4)%. The directionality of the amplifier protects the readout cavity and qubit from excess backaction caused by amplified vacuum fluctuations. In addition to providing tools for further improving the fidelity of strong projective measurement, this work creates a test bed for the experimental study of ideal weak measurements, and it opens the way toward quantum feedback protocols based on weak measurement such as state stabilization or error correction.
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Affiliation(s)
- F Lecocq
- National Institute of Standards and Technology, 325 Broadway, Boulder, Colorado 80305, USA
- Department of Physics, University of Colorado, 2000 Colorado Avenue, Boulder, Colorado 80309, USA
| | - L Ranzani
- Raytheon BBN Technologies, Cambridge, Massachusetts 02138, USA
| | - G A Peterson
- National Institute of Standards and Technology, 325 Broadway, Boulder, Colorado 80305, USA
- Department of Physics, University of Colorado, 2000 Colorado Avenue, Boulder, Colorado 80309, USA
| | - K Cicak
- National Institute of Standards and Technology, 325 Broadway, Boulder, Colorado 80305, USA
| | - X Y Jin
- National Institute of Standards and Technology, 325 Broadway, Boulder, Colorado 80305, USA
- Department of Physics, University of Colorado, 2000 Colorado Avenue, Boulder, Colorado 80309, USA
| | - R W Simmonds
- National Institute of Standards and Technology, 325 Broadway, Boulder, Colorado 80305, USA
| | - J D Teufel
- National Institute of Standards and Technology, 325 Broadway, Boulder, Colorado 80305, USA
| | - J Aumentado
- National Institute of Standards and Technology, 325 Broadway, Boulder, Colorado 80305, USA
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2
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Peterson GA, Kotler S, Lecocq F, Cicak K, Jin XY, Simmonds RW, Aumentado J, Teufel JD. Ultrastrong Parametric Coupling between a Superconducting Cavity and a Mechanical Resonator. Phys Rev Lett 2019; 123:247701. [PMID: 31922827 DOI: 10.1103/physrevlett.123.247701] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/26/2019] [Indexed: 06/10/2023]
Abstract
We present a new optomechanical device where the motion of a micromechanical membrane couples to a microwave resonance of a three-dimensional superconducting cavity. With this architecture, we realize ultrastrong parametric coupling, where the coupling not only exceeds the dissipation in the system but also rivals the mechanical frequency itself. In this regime, the optomechanical interaction induces a frequency splitting between the hybridized normal modes that reaches 88% of the bare mechanical frequency, limited by the fundamental parametric instability. The coupling also exceeds the mechanical thermal decoherence rate, enabling new applications in ultrafast quantum state transfer and entanglement generation.
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Affiliation(s)
- G A Peterson
- National Institute of Standards and Technology, 325 Broadway, Boulder, Colorado 80305, USA
- Department of Physics, University of Colorado, Boulder, Colorado 80309, USA
| | - S Kotler
- National Institute of Standards and Technology, 325 Broadway, Boulder, Colorado 80305, USA
- Department of Physics, University of Colorado, Boulder, Colorado 80309, USA
| | - F Lecocq
- National Institute of Standards and Technology, 325 Broadway, Boulder, Colorado 80305, USA
- Department of Physics, University of Colorado, Boulder, Colorado 80309, USA
| | - K Cicak
- National Institute of Standards and Technology, 325 Broadway, Boulder, Colorado 80305, USA
| | - X Y Jin
- National Institute of Standards and Technology, 325 Broadway, Boulder, Colorado 80305, USA
- Department of Physics, University of Colorado, Boulder, Colorado 80309, USA
| | - R W Simmonds
- National Institute of Standards and Technology, 325 Broadway, Boulder, Colorado 80305, USA
| | - J Aumentado
- National Institute of Standards and Technology, 325 Broadway, Boulder, Colorado 80305, USA
| | - J D Teufel
- National Institute of Standards and Technology, 325 Broadway, Boulder, Colorado 80305, USA
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3
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Menke T, Burns PS, Higginbotham AP, Kampel NS, Peterson RW, Cicak K, Simmonds RW, Regal CA, Lehnert KW. Reconfigurable re-entrant cavity for wireless coupling to an electro-optomechanical device. Rev Sci Instrum 2017; 88:094701. [PMID: 28964202 DOI: 10.1063/1.5000973] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/27/2017] [Accepted: 08/20/2017] [Indexed: 06/07/2023]
Abstract
An electro-optomechanical device capable of microwave-to-optics conversion has recently been demonstrated, with the vision of enabling optical networks of superconducting qubits. Here we present an improved converter design that uses a three-dimensional microwave cavity for coupling between the microwave transmission line and an integrated LC resonator on the converter chip. The new design simplifies the optical assembly and decouples it from the microwave part of the setup. Experimental demonstrations show that the modular device assembly allows us to flexibly tune the microwave coupling to the converter chip while maintaining small loss. We also find that electromechanical experiments are not impacted by the additional microwave cavity. Our design is compatible with a high-finesse optical cavity and will improve optical performance.
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Affiliation(s)
- T Menke
- Department of Physics, Harvard University, Cambridge, Massachusetts 02138, USA
| | - P S Burns
- JILA, University of Colorado and NIST, Boulder, Colorado 80309, USA
| | - A P Higginbotham
- JILA, University of Colorado and NIST, Boulder, Colorado 80309, USA
| | - N S Kampel
- JILA, University of Colorado and NIST, Boulder, Colorado 80309, USA
| | - R W Peterson
- JILA, University of Colorado and NIST, Boulder, Colorado 80309, USA
| | - K Cicak
- National Institute of Standards and Technology (NIST), Boulder, Colorado 80305, USA
| | - R W Simmonds
- National Institute of Standards and Technology (NIST), Boulder, Colorado 80305, USA
| | - C A Regal
- JILA, University of Colorado and NIST, Boulder, Colorado 80309, USA
| | - K W Lehnert
- JILA, University of Colorado and NIST, Boulder, Colorado 80309, USA
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4
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Lecocq F, Ranzani L, Peterson GA, Cicak K, Simmonds RW, Teufel JD, Aumentado J. Nonreciprocal Microwave Signal Processing with a Field-Programmable Josephson Amplifier. Phys Rev Appl 2017; 7:10.1103/physrevapplied.7.024028. [PMID: 38501125 PMCID: PMC10947609 DOI: 10.1103/physrevapplied.7.024028] [Citation(s) in RCA: 36] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 03/20/2024]
Abstract
We report on the design and implementation of a field-programmable Josephson amplifier (FPJA)-a compact and lossless superconducting circuit that can be programmed in situ by a set of microwave drives to perform reciprocal and nonreciprocal frequency conversion and amplification. In this work, we demonstrate four modes of operation: frequency conversion (transmission of -0.5 dB, reflection of -30 dB), circulation (transmission of -0.5 dB, reflection of -30 dB, isolation of 30 dB), phase-preserving amplification (gain > 20 dB, one photon of added noise) and directional phase-preserving amplification (reflection of -10 dB, forward gain of 18 dB, reverse isolation of 8 dB, one photon of added noise). The system exhibits quantitative agreement with the theoretical prediction. Based on a gradiometric superconducting quantum-interference device with Nb / Al - AlO x / Nb Josephson junctions, the FPJA is first-order insensitive to flux noise and can be operated without magnetic shielding at low temperature. Owing to its flexible design and compatibility with existing superconducting fabrication techniques, the FPJA offers a straightforward route toward on-chip integration with superconducting quantum circuits such as qubits and microwave optomechanical systems.
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Affiliation(s)
- F. Lecocq
- National Institute of Standards and Technology, 325 Broadway, Boulder, Colorado 80305, USA
| | - L. Ranzani
- Raytheon BBN Technologies, 10 Moulton Street, Cambridge, Massachusetts 02138, USA
| | - G. A. Peterson
- National Institute of Standards and Technology, 325 Broadway, Boulder, Colorado 80305, USA
| | - K. Cicak
- National Institute of Standards and Technology, 325 Broadway, Boulder, Colorado 80305, USA
| | - R. W. Simmonds
- National Institute of Standards and Technology, 325 Broadway, Boulder, Colorado 80305, USA
| | - J. D. Teufel
- National Institute of Standards and Technology, 325 Broadway, Boulder, Colorado 80305, USA
| | - J. Aumentado
- National Institute of Standards and Technology, 325 Broadway, Boulder, Colorado 80305, USA
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5
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Lecocq F, Clark JB, Simmonds RW, Aumentado J, Teufel JD. Mechanically Mediated Microwave Frequency Conversion in the Quantum Regime. Phys Rev Lett 2016; 116:043601. [PMID: 26871329 DOI: 10.1103/physrevlett.116.043601] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/22/2015] [Indexed: 06/05/2023]
Abstract
We report the observation of efficient and low-noise frequency conversion between two microwave modes, mediated by the motion of a mechanical resonator subjected to radiation pressure. We achieve coherent conversion of more than 10^{12} photons/s with a 95% efficiency and a 14 kHz bandwidth. With less than 10^{-1} photons·s^{-1}·Hz^{-1} of added noise, this optomechanical frequency converter is suitable for quantum state transduction. We show the ability to operate this converter as a tunable beam splitter, with direct applications for photon routing and communication through complex quantum networks.
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Affiliation(s)
- F Lecocq
- National Institute of Standards and Technology, 325 Broadway, Boulder, Colorado 80305, USA
| | - J B Clark
- National Institute of Standards and Technology, 325 Broadway, Boulder, Colorado 80305, USA
| | - R W Simmonds
- National Institute of Standards and Technology, 325 Broadway, Boulder, Colorado 80305, USA
| | - J Aumentado
- National Institute of Standards and Technology, 325 Broadway, Boulder, Colorado 80305, USA
| | - J D Teufel
- National Institute of Standards and Technology, 325 Broadway, Boulder, Colorado 80305, USA
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6
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Teufel JD, Lecocq F, Simmonds RW. Overwhelming Thermomechanical Motion with Microwave Radiation Pressure Shot Noise. Phys Rev Lett 2016; 116:013602. [PMID: 26799018 DOI: 10.1103/physrevlett.116.013602] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/20/2015] [Indexed: 06/05/2023]
Abstract
We measure the fundamental noise processes associated with a continuous linear position measurement of a micromechanical membrane incorporated in a microwave cavity optomechanical circuit. We observe the trade-off between the two fundamental sources of noise that enforce the standard quantum limit: the measurement imprecision and radiation pressure backaction from photon shot noise. We demonstrate that the quantum backaction of the measurement can overwhelm the intrinsic thermal motion by 24 dB, entering a new regime for cavity optomechanical systems.
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Affiliation(s)
- J D Teufel
- National Institute of Standards and Technology, 325 Broadway, Boulder, Colorado 80305, USA
| | - F Lecocq
- National Institute of Standards and Technology, 325 Broadway, Boulder, Colorado 80305, USA
| | - R W Simmonds
- National Institute of Standards and Technology, 325 Broadway, Boulder, Colorado 80305, USA
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7
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Allman MS, Whittaker JD, Castellanos-Beltran M, Cicak K, da Silva F, DeFeo MP, Lecocq F, Sirois A, Teufel JD, Aumentado J, Simmonds RW. Tunable resonant and nonresonant interactions between a phase qubit and LC resonator. Phys Rev Lett 2014; 112:123601. [PMID: 24724648 DOI: 10.1103/physrevlett.112.123601] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/24/2013] [Indexed: 06/03/2023]
Abstract
We use a flux-biased radio frequency superconducting quantum interference device (rf SQUID) with an embedded flux-biased direct current SQUID to generate strong resonant and nonresonant tunable interactions between a phase qubit and a lumped-element resonator. The rf SQUID creates a tunable magnetic susceptibility between the qubit and resonator providing resonant coupling strengths from zero to near the ultrastrong coupling regime. By modulating the magnetic susceptibility, nonresonant parametric coupling achieves rates >100 MHz. Nonlinearity of the magnetic susceptibility also leads to parametric coupling at the subharmonics of the qubit-resonator detuning.
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Affiliation(s)
- M S Allman
- National Institute of Standards and Technology, 325 Broadway Street, Boulder, Colorado 80305-3328, USA
| | - J D Whittaker
- National Institute of Standards and Technology, 325 Broadway Street, Boulder, Colorado 80305-3328, USA
| | - M Castellanos-Beltran
- National Institute of Standards and Technology, 325 Broadway Street, Boulder, Colorado 80305-3328, USA
| | - K Cicak
- National Institute of Standards and Technology, 325 Broadway Street, Boulder, Colorado 80305-3328, USA
| | - F da Silva
- National Institute of Standards and Technology, 325 Broadway Street, Boulder, Colorado 80305-3328, USA
| | - M P DeFeo
- National Institute of Standards and Technology, 325 Broadway Street, Boulder, Colorado 80305-3328, USA
| | - F Lecocq
- National Institute of Standards and Technology, 325 Broadway Street, Boulder, Colorado 80305-3328, USA
| | - A Sirois
- National Institute of Standards and Technology, 325 Broadway Street, Boulder, Colorado 80305-3328, USA
| | - J D Teufel
- National Institute of Standards and Technology, 325 Broadway Street, Boulder, Colorado 80305-3328, USA
| | - J Aumentado
- National Institute of Standards and Technology, 325 Broadway Street, Boulder, Colorado 80305-3328, USA
| | - R W Simmonds
- National Institute of Standards and Technology, 325 Broadway Street, Boulder, Colorado 80305-3328, USA
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8
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9
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Teufel JD, Donner T, Li D, Harlow JW, Allman MS, Cicak K, Sirois AJ, Whittaker JD, Lehnert KW, Simmonds RW. Sideband cooling of micromechanical motion to the quantum ground state. Nature 2011; 475:359-63. [DOI: 10.1038/nature10261] [Citation(s) in RCA: 1527] [Impact Index Per Article: 117.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2011] [Accepted: 06/02/2011] [Indexed: 11/09/2022]
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10
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Teufel JD, Li D, Allman MS, Cicak K, Sirois AJ, Whittaker JD, Simmonds RW. Circuit cavity electromechanics in the strong-coupling regime. Nature 2011; 471:204-8. [PMID: 21390127 DOI: 10.1038/nature09898] [Citation(s) in RCA: 622] [Impact Index Per Article: 47.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2010] [Accepted: 01/31/2011] [Indexed: 11/10/2022]
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11
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Allman MS, Altomare F, Whittaker JD, Cicak K, Li D, Sirois A, Strong J, Teufel JD, Simmonds RW. rf-SQUID-mediated coherent tunable coupling between a superconducting phase qubit and a lumped-element resonator. Phys Rev Lett 2010; 104:177004. [PMID: 20482130 DOI: 10.1103/physrevlett.104.177004] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/06/2010] [Indexed: 05/29/2023]
Abstract
We demonstrate coherent tunable coupling between a superconducting phase qubit and a lumped-element resonator. The coupling strength is mediated by a flux-biased rf SQUID operated in the nonhysteretic regime. By tuning the applied flux bias to the rf SQUID we change the effective mutual inductance, and thus the coupling energy, between the phase qubit and resonator. We verify the modulation of coupling strength from 0 to 100 MHz by observing modulation in the size of the splitting in the phase qubit's spectroscopy, as well as coherently by observing modulation in the vacuum Rabi oscillation frequency when on resonance. The measured spectroscopic splittings and vacuum Rabi oscillations agree well with theoretical predictions.
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Affiliation(s)
- M S Allman
- National Institute of Standards and Technology, 325 Broadway, Boulder, Colorado 80305-3328, USA
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12
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Abstract
The high-Q harmonic oscillator mode of a Josephson junction can be used as a novel probe of spurious two-level systems (TLSs) inside the amorphous oxide tunnel barrier of the junction. In particular, we show that spectroscopic transmission measurements of the junction resonator mode can reveal how the coupling magnitude between the junction and the TLSs varies with an external magnetic field applied in the plane of the tunnel barrier. The proposed experiments offer the possibility of clearly resolving the underlying coupling mechanism for these spurious TLSs, an important decoherence source limiting the quality of superconducting quantum devices.
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Affiliation(s)
- L Tian
- Department of Applied Physics and E. L. Ginzton Laboratory, Stanford University, Stanford, California 94305, USA.
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13
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Martinis JM, Cooper KB, McDermott R, Steffen M, Ansmann M, Osborn KD, Cicak K, Oh S, Pappas DP, Simmonds RW, Yu CC. Decoherence in Josephson qubits from dielectric loss. Phys Rev Lett 2005; 95:210503. [PMID: 16384123 DOI: 10.1103/physrevlett.95.210503] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/21/2005] [Indexed: 05/05/2023]
Abstract
Dielectric loss from two-level states is shown to be a dominant decoherence source in superconducting quantum bits. Depending on the qubit design, dielectric loss from insulating materials or the tunnel junction can lead to short coherence times. We show that a variety of microwave and qubit measurements are well modeled by loss from resonant absorption of two-level defects. Our results demonstrate that this loss can be significantly reduced by using better dielectrics and fabricating junctions of small area . With a redesigned phase qubit employing low-loss dielectrics, the energy relaxation rate has been improved by a factor of 20, opening up the possibility of multiqubit gates and algorithms.
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Affiliation(s)
- John M Martinis
- Department of Physics, University of California, Santa Barbara, California 93106, USA
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14
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McDermott R, Simmonds RW, Steffen M, Cooper KB, Cicak K, Osborn KD, Oh S, Pappas DP, Martinis JM. Simultaneous State Measurement of Coupled Josephson Phase Qubits. Science 2005; 307:1299-302. [PMID: 15731451 DOI: 10.1126/science.1107572] [Citation(s) in RCA: 247] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
One of the many challenges of building a scalable quantum computer is single-shot measurement of all the quantum bits (qubits). We have used simultaneous single-shot measurement of coupled Josephson phase qubits to directly probe interaction of the qubits in the time domain. The concept of measurement crosstalk is introduced, and we show that its effects are minimized by careful adjustment of the timing of the measurements. We observe the antiphase oscillation of the two-qubit 01 and 10 states, consistent with quantum mechanical entanglement of these states, thereby opening the possibility for full characterization of multiqubit gates and elementary quantum algorithms.
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Affiliation(s)
- R McDermott
- Department of Physics, University of California, Santa Barbara, CA 93106, USA
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15
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Cooper KB, Steffen M, McDermott R, Simmonds RW, Oh S, Hite DA, Pappas DP, Martinis JM. Observation of quantum oscillations between a Josephson phase qubit and a microscopic resonator using fast readout. Phys Rev Lett 2004; 93:180401. [PMID: 15525134 DOI: 10.1103/physrevlett.93.180401] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/27/2004] [Indexed: 05/24/2023]
Abstract
We have detected coherent quantum oscillations between Josephson phase qubits and critical-current fluctuators by implementing a new state readout technique that is an order of magnitude faster than previous methods. These results reveal a new aspect of the quantum behavior of Josephson junctions, and they demonstrate the means to measure two-qubit interactions in the time domain. The junction-fluctuator interaction also points to a possible mechanism for decoherence and reduced fidelity in superconducting qubits.
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Affiliation(s)
- K B Cooper
- National Institute of Standards and Technology, 325 Broadway, Boulder, CO 80305, USA
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16
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Simmonds RW, Lang KM, Hite DA, Nam S, Pappas DP, Martinis JM. Decoherence in josephson phase qubits from junction resonators. Phys Rev Lett 2004; 93:077003. [PMID: 15324267 DOI: 10.1103/physrevlett.93.077003] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/12/2003] [Indexed: 05/24/2023]
Abstract
Although Josephson junction qubits show great promise for quantum computing, the origin of dominant decoherence mechanisms remains unknown. Improving the operation of a Josephson junction based phase qubit has revealed microscopic two-level systems or resonators within the tunnel barrier that cause decoherence. We report spectroscopic data that show a level splitting characteristic of coupling between a two-state qubit and a two-level system. Furthermore, we show Rabi oscillations whose "coherence amplitude" is significantly degraded by the presence of these spurious microwave resonators. The discovery of these resonators impacts the future of Josephson qubits as well as existing Josephson technologies.
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Affiliation(s)
- R W Simmonds
- National Institute of Standards and Technology, 325 Broadway, Boulder, Colorado 80305-3328, USA
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17
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McElroy K, Simmonds RW, Hoffman JE, Lee DH, Orenstein J, Eisaki H, Uchida S, Davis JC. Relating atomic-scale electronic phenomena to wave-like quasiparticle states in superconducting Bi2Sr2CaCu2O8+delta. Nature 2003; 422:592-6. [PMID: 12686994 DOI: 10.1038/nature01496] [Citation(s) in RCA: 398] [Impact Index Per Article: 19.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2002] [Accepted: 02/14/2003] [Indexed: 11/09/2022]
Abstract
The electronic structure of simple crystalline solids can be completely described in terms either of local quantum states in real space (r-space), or of wave-like states defined in momentum-space (k-space). However, in the copper oxide superconductors, neither of these descriptions alone may be sufficient. Indeed, comparisons between r-space and k-space studies of Bi2Sr2CaCu2O8+delta (Bi-2212) reveal numerous unexplained phenomena and apparent contradictions. Here, to explore these issues, we report Fourier transform studies of atomic-scale spatial modulations in the Bi-2212 density of states. When analysed as arising from quasiparticle interference, the modulations yield elements of the Fermi-surface and energy gap in agreement with photoemission experiments. The consistency of numerous sets of dispersing modulations with the quasiparticle interference model shows that no additional order parameter is required. We also explore the momentum-space structure of the unoccupied states that are inaccessible to photoemission, and find strong similarities to the structure of the occupied states. The copper oxide quasiparticles therefore apparently exhibit particle-hole mixing similar to that of conventional superconductors. Near the energy gap maximum, the modulations become intense, commensurate with the crystal, and bounded by nanometre-scale domains. Scattering of the antinodal quasiparticles is therefore strongly influenced by nanometre-scale disorder.
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Affiliation(s)
- K McElroy
- Department of Physics, University of California, and Materials Science Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
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18
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Simmonds RW, Marchenkov A, Davis JC, Packard RE. Observation of the superfluid shapiro effect in a 3He weak link. Phys Rev Lett 2001; 87:035301. [PMID: 11461563 DOI: 10.1103/physrevlett.87.035301] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/26/2001] [Indexed: 05/23/2023]
Abstract
We have studied the mass currents through a superfluid 3He Josephson weak link in the presence of an externally applied ac pressure modulation. Characteristic changes in the dc mass currents are observed whenever the superfluid Josephson frequency omega(J) is an integer multiple of the ac modulation frequency omega. The measured dependencies of these current changes on ac pressure amplitude are in excellent agreement with theory describing quantum phase dynamics of superfluid 3He weak links. These results establish the superfluid analog of the superconducting Shapiro effect.
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Affiliation(s)
- R W Simmonds
- Department of Physics, University of California, Berkeley, California 94720, USA
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19
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Abstract
Celebrated interference experiments have demonstrated the wave nature of light and electrons, quantum interference being the manifestation of wave-particle duality. More recently, double-path interference experiments have also demonstrated the quantum-wave nature of beams of neutrons, atoms and Bose-Einstein condensates. In condensed matter systems, double-path quantum interference is observed in the d.c. superconducting quantum interference device (d.c. SQUID). Here we report a double-path quantum interference experiment involving a liquid: superfluid 3He. Using a geometry analogous to the superconducting d.c. SQUID, we control a quantum phase shift by using the rotation of the Earth, and find the classic interference pattern with periodicity determined by the 3He quantum of circulation.
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Affiliation(s)
- R W Simmonds
- Physics Department, University of California, Berkeley 94720, USA
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20
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Simmonds RW, Marchenkov A, Vitale S, Davis JC, Packard RE. New flow dissipation mechanisms in superfluid 3He. Phys Rev Lett 2000; 84:6062-6065. [PMID: 10991124 DOI: 10.1103/physrevlett.84.6062] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/01/2000] [Indexed: 05/23/2023]
Abstract
We have studied the flow of superfluid 3He-B forced through small apertures. There are unexpectedly large dissipative currents, which can be described by two independent processes. One process involves the creation of quasiparticles within the aperture and their subsequent acceleration in the ambient pressure gradient. The second process involves the dissipative precession of a texture in a geometry-induced anisotropic order parameter. For both mechanisms we make a simple estimate of the relevant effect and find these agree well with the data.
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Affiliation(s)
- R W Simmonds
- Physics Department, University of California, Berkeley, California 94720, USA
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