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Mills SM, Averin DV, Du X. Localizing Fractional Quasiparticles on Graphene Quantum Hall Antidots. Phys Rev Lett 2020; 125:227701. [PMID: 33315430 DOI: 10.1103/physrevlett.125.227701] [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: 03/27/2020] [Accepted: 10/26/2020] [Indexed: 06/12/2023]
Abstract
We report localization of fractional quantum Hall (QH) quasiparticles on graphene antidots. By studying coherent tunneling through the localized QH edge modes on the antidot, we measured the QH quasiparticle charges to be approximately ±e/3 at fractional fillings of ν=±1/3. The Dirac spectrum in graphene allows large energy scales and robust quasiparticle localization against thermal excitation. The capability of localizing fractional quasiparticles on QH antidots brings promising opportunities for realizing anyon braiding and novel quantum electronics.
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Affiliation(s)
- S M Mills
- Department of Physics, Stony Brook University, Stony Brook, New York 11794, USA
| | - D V Averin
- Department of Physics, Stony Brook University, Stony Brook, New York 11794, USA
| | - X Du
- Department of Physics, Stony Brook University, Stony Brook, New York 11794, USA
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Averin DV, Xu K, Zhong YP, Song C, Wang H, Han S. Suppression of Dephasing by Qubit Motion in Superconducting Circuits. Phys Rev Lett 2016; 116:010501. [PMID: 26799006 DOI: 10.1103/physrevlett.116.010501] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/31/2015] [Indexed: 06/05/2023]
Abstract
We suggest and demonstrate a protocol which suppresses the low-frequency dephasing by qubit motion, i.e., transfer of the logical qubit of information in a system of n≥2 physical qubits. The protocol requires only the nearest-neighbor coupling and is applicable to different qubit structures. Our analysis of its effectiveness against noises with arbitrary correlations, together with experiments using up to three superconducting qubits, shows that for the realistic uncorrelated noises, qubit motion increases the dephasing time of the logical qubit as √n. In general, the protocol provides a diagnostic tool for measurements of the noise correlations.
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Affiliation(s)
- D V Averin
- Department of Physics and Astronomy, Stony Brook University, SUNY, Stony Brook, New York 11794-3800, USA
| | - K Xu
- Department of Physics, Zhejiang University, Hangzhou, Zhejiang 310027, China
| | - Y P Zhong
- Department of Physics, Zhejiang University, Hangzhou, Zhejiang 310027, China
| | - C Song
- Department of Physics, Zhejiang University, Hangzhou, Zhejiang 310027, China
| | - H Wang
- Department of Physics, Zhejiang University, Hangzhou, Zhejiang 310027, China
| | - Siyuan Han
- Department of Physics and Astronomy, University of Kansas, Lawrence, Kansas 66045, USA
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Saira OP, Yoon Y, Tanttu T, Möttönen M, Averin DV, Pekola JP. Test of the Jarzynski and Crooks fluctuation relations in an electronic system. Phys Rev Lett 2012; 109:180601. [PMID: 23215263 DOI: 10.1103/physrevlett.109.180601] [Citation(s) in RCA: 67] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/26/2012] [Indexed: 06/01/2023]
Abstract
Recent progress on micro- and nanometer-scale manipulation has opened the possibility to probe systems small enough that thermal fluctuations of energy and coordinate variables can be significant compared with their mean behavior. We present an experimental study of nonequilibrium thermodynamics in a classical two-state system, namely, a metallic single-electron box. We have measured with high statistical accuracy the distribution of dissipated energy as single electrons are transferred between the box electrodes. The obtained distributions obey Jarzynski and Crooks fluctuation relations. A comprehensive microscopic theory exists for the system, enabling the experimental distributions to be reproduced without fitting parameters.
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Affiliation(s)
- O-P Saira
- Low Temperature Laboratory, OVLL, Aalto University, PO Box 15100, FI-00076 Aalto, Finland
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Maisi VF, Saira OP, Pashkin YA, Tsai JS, Averin DV, Pekola JP. Real-time observation of discrete Andreev tunneling events. Phys Rev Lett 2011; 106:217003. [PMID: 21699331 DOI: 10.1103/physrevlett.106.217003] [Citation(s) in RCA: 5] [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: 02/28/2011] [Indexed: 05/31/2023]
Abstract
We provide a direct proof of two-electron Andreev transitions in a superconductor-normal-metal tunnel junction by detecting them in a real-time electron counting experiment. Our results are consistent with ballistic Andreev transport with an order of magnitude higher rate than expected for a uniform barrier, suggesting that only part of the interface is effectively contributing to the transport. These findings are quantitatively supported by our direct current measurements in single-electron transistors with similar tunnel barriers.
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Affiliation(s)
- V F Maisi
- Low Temperature Laboratory, Aalto University, P.O. Box 13500, 00076 Aalto, Finland.
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Harris R, Johnson MW, Han S, Berkley AJ, Johansson J, Bunyk P, Ladizinsky E, Govorkov S, Thom MC, Uchaikin S, Bumble B, Fung A, Kaul A, Kleinsasser A, Amin MHS, Averin DV. Probing noise in flux qubits via macroscopic resonant tunneling. Phys Rev Lett 2008; 101:117003. [PMID: 18851318 DOI: 10.1103/physrevlett.101.117003] [Citation(s) in RCA: 6] [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: 12/13/2007] [Indexed: 05/26/2023]
Abstract
Macroscopic resonant tunneling between the two lowest lying states of a bistable rf SQUID is used to characterize noise in a flux qubit. Measurements of the incoherent decay rate as a function of flux bias revealed a Gaussian-shaped profile that is not peaked at the resonance point but is shifted to a bias at which the initial well is higher than the target well. The rms amplitude of the noise, which is proportional to the dephasing rate 1/tauphi, was observed to be weakly dependent on temperature below 70 mK. Analysis of these results indicates that the dominant source of low energy flux noise in this device is a quantum mechanical environment in thermal equilibrium.
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Affiliation(s)
- R Harris
- D-Wave Systems Inc., 100-4401 Still Creek Drive, Burnaby, BC V5C 6G9, Canada.
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Abstract
We propose and investigate a novel method for the controlled coupling of two Josephson charge qubits by means of a variable electrostatic transformer. The value of the coupling capacitance is given by the discretized curvature of the lowest energy band of a Josephson junction, which can be positive, negative, or zero. We calculate the charging diagram of the two-qubit system that reflects the transition from positive to negative through vanishing coupling. We also discuss how to implement a phase gate making use of the controllable coupling.
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Affiliation(s)
- D V Averin
- Department of Physics and Astronomy, University of Stony Brook, SUNY, Stony Brook, New York 11794-3800, USA
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Pashkin YA, Yamamoto T, Astafiev O, Nakamura Y, Averin DV, Tsai JS. Quantum oscillations in two coupled charge qubits. Nature 2003; 421:823-6. [PMID: 12594507 DOI: 10.1038/nature01365] [Citation(s) in RCA: 618] [Impact Index Per Article: 29.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2002] [Accepted: 12/10/2002] [Indexed: 11/09/2022]
Abstract
A practical quantum computer, if built, would consist of a set of coupled two-level quantum systems (qubits). Among the variety of qubits implemented, solid-state qubits are of particular interest because of their potential suitability for integrated devices. A variety of qubits based on Josephson junctions have been implemented; these exploit the coherence of Cooper-pair tunnelling in the superconducting state. Despite apparent progress in the implementation of individual solid-state qubits, there have been no experimental reports of multiple qubit gates--a basic requirement for building a real quantum computer. Here we demonstrate a Josephson circuit consisting of two coupled charge qubits. Using a pulse technique, we coherently mix quantum states and observe quantum oscillations, the spectrum of which reflects interaction between the qubits. Our results demonstrate the feasibility of coupling multiple solid-state qubits, and indicate the existence of entangled two-qubit states.
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Affiliation(s)
- Yu A Pashkin
- The Institute of Physical and Chemical Research (RIKEN), Wako, Saitama 351-0198, Japan
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Abstract
The concept of quantum nondemolition (QND) measurement is extended to coherent oscillations in an individual two-state system. Such a measurement enables direct observation of an intrinsic spectrum of these oscillations avoiding the detector-induced dephasing that affects the standard (non-QND) measurements. The suggested scheme can be realized in Josephson-junction qubits which combine flux and charge dynamics.
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Affiliation(s)
- D V Averin
- Department of Physics and Astronomy, SUNY Stony Brook, Stony Brook, New York 11794-3800, USA
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Abstract
We suggest a system in which the amplitude of macroscopic flux tunneling can be modulated via the Aharonov-Casher effect. The system is an rf SQUID with the Josephson junction replaced by a Bloch transistor--two junctions separated by a small superconducting island on which the charge can be induced by an external gate voltage. When the Josephson coupling energies of the junctions are equal and the induced charge is q = e, destructive interference between tunneling paths brings the flux tunneling rate to zero. The device may also be useful as a qubit for quantum computation.
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Affiliation(s)
- Jonathan R Friedman
- Department of Physics and Astronomy, The State University of New York at Stony Brook, Stony Brook, New York 11794-3800, USA
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Naveh Y, Patel V, Averin DV, Likharev KK, Lukens JE. Universal distribution of transparencies in highly conductive Nb/AlO(x)/Nb junctions. Phys Rev Lett 2000; 85:5404-5407. [PMID: 11136007 DOI: 10.1103/physrevlett.85.5404] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/09/2000] [Indexed: 05/23/2023]
Abstract
We report the observation of the universal distribution of transparencies, predicted by Schep and Bauer [Phys. Rev. Lett. 78, 3015 (1997)] for dirty sharp interfaces, in uniform Nb/AlO(x)/Nb junctions with high specific conductance (10(8) ohm(-1) cm(-2)). Experiments used the BCS density of states in superconducting niobium for transparency distribution probing. Experimental results for both the dc I-V curves at magnetic-field-suppressed supercurrent and the Josephson critical current in zero magnetic field coincide remarkably well with calculations based on the multimode theory of multiple Andreev reflections and the Schep-Bauer distribution.
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Affiliation(s)
- Y Naveh
- Department of Physics and Astronomy, State University of New York, Stony Brook, New York 11794-3800, USA
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Abstract
We have analyzed Coulomb drag between currents of interacting electrons in two parallel one-dimensional conductors of finite length L attached to external reservoirs. For strong coupling, the relative fluctuations of electron density in the conductors acquire energy gap M. At energies larger than gamma = constxv(-)exp(-LM/v(-))/L+gamma(+), where gamma(+) is the impurity scattering rate, and, for L>v(-)/M, where v(-) is the fluctuation velocity, the gap leads to an "ideal" drag with almost equal currents in the conductors. At low energies the drag is suppressed by coherent instanton tunneling, and the zero-temperature transconductance vanishes, indicating the Fermi-liquid behavior.
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Affiliation(s)
- VV Ponomarenko
- Department of Physics and Astronomy, SUNY Stony Brook, Stony Brook, New York 11794, USA
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Korotkov AN, Averin DV, Likharev KK. Statistical properties of continuous-wave Bloch oscillations in double-well semiconductor heterostructures. Phys Rev B Condens Matter 1994; 49:7548-7556. [PMID: 10009496 DOI: 10.1103/physrevb.49.7548] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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Averin DV, Nazarov YV. Single-electron oscillations in the one-dimensional interacting electron gas. Phys Rev B Condens Matter 1994; 49:2951-2954. [PMID: 10011139 DOI: 10.1103/physrevb.49.2951] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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Korotkov AN, Averin DV, Likharev KK. Combined Bloch and single-electron-tunneling oscillations in one-dimensional arrays of small tunnel junctions. Phys Rev B Condens Matter 1994; 49:1915-1918. [PMID: 10010990 DOI: 10.1103/physrevb.49.1915] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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Averin DV, Korotkov AN, Likharev KK. Theory of single-electron charging of quantum wells and dots. Phys Rev B Condens Matter 1991; 44:6199-6211. [PMID: 9998482 DOI: 10.1103/physrevb.44.6199] [Citation(s) in RCA: 201] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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Averin DV, Korotkov AN, Nazarov YV. Transport of electron-hole pairs in arrays of small tunnel junctions. Phys Rev Lett 1991; 66:2818-2821. [PMID: 10043624 DOI: 10.1103/physrevlett.66.2818] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
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Geerligs LJ, Averin DV, Mooij JE. Observation of macroscopic quantum tunneling through the Coulomb energy barrier. Phys Rev Lett 1990; 65:3037-3040. [PMID: 10042763 DOI: 10.1103/physrevlett.65.3037] [Citation(s) in RCA: 26] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
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