Observation of the Aharonov-Casher effect for vortices in Josephson-junction arrays

Elion, W.J.; Wachters, J.J.; Sohn, Lydia L.; Mooij, J. E.

doi:10.1103/physrevlett.71.2311

Cited by 118 publications

(66 citation statements)

References 16 publications

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“…An alternative is to use Josephson vortices (fluxons), which arise due to phase-slip events in Josephson junctions [24,25]. Their effective mass is determined by the charging and Josephson energies of the junction and can be much smaller than that of Abrikosov vortices, allowing them to behave quantum-mechanically [26,27]. Indeed, the AharonovCasher effect with Josephson vortices has been experimentally observed [26] and several proposals have been made to utilize it in the context of topological quantum information processing [14,[28][29][30].…”

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confidence: 99%

Topological Quantum Buses: Coherent Quantum Information Transfer between Topological and Conventional Qubits

2011

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We propose computing bus devices that enable quantum information to be coherently transferred between topological and conventional qubits. We describe a concrete realization of such a topological quantum bus acting between a topological qubit in a Majorana wire network and a conventional semiconductor double quantum dot qubit. Specifically, this device measures the joint (fermion) parity of these two different qubits by using the Aharonov-Casher effect in conjunction with an ancilliary superconducting flux qubit that facilitates the measurement. Such a parity measurement, together with the ability to apply Hadamard gates to the two qubits, allows one to produce states in which the topological and conventional qubits are maximally entangled and to teleport quantum states between the topological and conventional quantum systems. Introduction.-The topological approach to quantum information processing obtains its exceptional faulttolerance by encoding and manipulating information in non-local (topological) degrees of freedom of topologically ordered systems [1][2][3]. These non-local degrees of freedom do not couple to local operations, so the error rates for topological qubits and computational gates are exponentially suppressed with distance between anyons and inverse temperature, providing an enormous advantage over conventional quantum computing platforms. However, the same fact also makes it very challenging to coherently transfer quantum information into and out of topological systems, since this not only requires coupling the non-local degrees of freedom in the topological system to an external system, but doing so in a controlled and coherent manner. In other words, one must be able to create quantum entanglement between the topological and conventional states. In this letter, we propose a device that can entangle and coherently transfer quantum information between topological and conventional quantum media, i.e. a "topological quantum bus." Such devices would allow one to harness the relative strengths of the different quantum media and could prove crucial for the implementation of quantum computation.

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Topological Quantum Buses: Coherent Quantum Information Transfer between Topological and Conventional Qubits

2011

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“…For example, the wave function of the flux vortices (fluxons) moving in such a network should acquire a phase that depends on the charge on superconducting islands [5]. Indeed, oscillations of the network resistance in the flux-flow regime have been observed as a function of the gate-induced island charge [6]; these oscillations have been attributed to the interference associated with the AC phase. However, this attribution is not unambiguous, because qualitatively similar phenomena can be produced by the Coulomb-blockade effect due to the quantization of charge on the superconducting islands [7].…”

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Spectroscopic Evidence of the Aharonov-Casher Effect in a Cooper Pair Box

et al. 2016

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We have observed the effect of the Aharonov-Casher (AC) interference on the spectrum of a superconducting system containing a symmetric Cooper pair box (CPB) and a large inductance. By varying the charge ng induced on the CPB island, we observed oscillations of the device spectrum with the period ∆ng = 2e. These oscillations are attributed to the charge-controlled AC interference between the fluxon tunneling processes in the CPB Josephson junctions. The measured phase and charge dependences of the frequencies of the |0 → |1 and |0 → |2 transitions are in good agreement with our numerical simulations. Almost complete suppression of the tunneling due to destructive interference has been observed for the charge ng = e(2n + 1). The CPB in this regime enables fluxon pairing, which can be used for the development of parity-protected superconducting qubits.The Aharonov-Casher (AC) effect is a non-local topological effect: the wave function of a neutral particle with magnetic moment moving in two dimensions around a charge acquires a phase shift proportional to the charge [1]. This effect has been observed in experiments with neutrons, atoms, and solid-state semiconductor systems (see, e.g., [2][3][4] and references therein). Similar effects have been predicted for superconducting networks of nanoscale superconducting islands coupled by Josephson junctions. For example, the wave function of the flux vortices (fluxons) moving in such a network should acquire a phase that depends on the charge on superconducting islands [5]. Indeed, oscillations of the network resistance in the flux-flow regime have been observed as a function of the gate-induced island charge [6]; these oscillations have been attributed to the interference associated with the AC phase. However, this attribution is not unambiguous, because qualitatively similar phenomena can be produced by the Coulomb-blockade effect due to the quantization of charge on the superconducting islands [7].More recently, indirect evidence for the AC effect in superconducting circuits has been obtained in the study of suppression of the macroscopic phase coherence in onedimensional (1D) chains of Josephson junctions by quantum fluctuations [8]. The quantum phase slips (QPS) in the junctions can be viewed as the charge-sensitive fluxon tunneling [9,10] provided the conditions discussed below are satisfied. Microwave experiments [11] have demonstrated that dephasing of a fluxonium, a small Josephson junction shunted by a 1D Josephson chain, can be due to the effect of fluctuating charges on the QPS in the chain. Applications of the AC effect in classical Josephson devices have been discussed in Refs. [7,12].In this Letter we describe microwave experiments which provide direct evidence for the charge-dependent interference between the amplitudes of fluxon tunneling. We have studied the microwave resonances of the device consisting of two nominally identical Josephson junctions separated by a nanoscale superconducting island (the socalled Cooper-pair box, CPB) and a large inductanc...

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“…For example, if the trapped vortices behave as complex quantum mechanical particles, this system may possess macroscopic quantum coherence and form macroscopic energy levels, which can then be measured by radio or microwave measurements [37]. Furthermore, if the trapped vortex can perform coherent quantum motion, detection of the Aharonov-Casher interference of Abrikosov vortices may be attempted [38,39]. From a technological perspective, the controlled manipulation of Abrikosov vortices within mesoscopic superconducting devices lays the groundwork for a variety of superconducting electronics [7][8][9].…”

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Vortex crossing and trapping in doubly connected mesoscopic loops of a single-crystal type-II superconductor

Mills

Shen

et al. 2015

Phys. Rev. B

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Numerical calculations on a mesoscopic ring of a type II superconductor in the London limit suggest that an Abrikosov vortex can be trapped in such a structure above a critical magnetic field and generate a phase shift in the magnetoresistance oscillations. We prepared submicron-sized superconducting loops of single-crystal, type II superconductor NbSe2 and measured magnetoresistance oscillations resulting from vortices crossing the loops. The free energy barrier for vortex crossing determines the crossing rate and is periodically modulated by the external magnetic flux threading the loop. We demonstrated experimentally that the crossing of vortices can be directed at a pair of constrictions in the loop, leading to more pronounced magnetoresistance oscillations than those in a uniform ring. The vortex trapping in both a simple ring and a ring featuring two constrictions was found to result in a phase shift in the magnetoresistance oscillations as predicted in the numerical calculations. The controlled crossing and trapping of vortices demonstrated in our NbSe2 devices provide a starting point for the manipulation of individual Abrikosov vortices, which is useful for future technologies.

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Observation of the Aharonov-Casher effect for vortices in Josephson-junction arrays

Cited by 118 publications

References 16 publications

Topological Quantum Buses: Coherent Quantum Information Transfer between Topological and Conventional Qubits

Topological Quantum Buses: Coherent Quantum Information Transfer between Topological and Conventional Qubits

Spectroscopic Evidence of the Aharonov-Casher Effect in a Cooper Pair Box

Vortex crossing and trapping in doubly connected mesoscopic loops of a single-crystal type-II superconductor

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