Dynamics of superconducting nanowires shunted with an external resistor

Brenner, Matthew; Roy, Dibyendu; Shah, Nayana; Bezryadin, Alexey

doi:10.1103/physrevb.85.224507

Cited by 43 publications

(59 citation statements)

References 67 publications

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“…For this purpose, we need to know approximate values of the effective shunt capacitance, the shunt impedance, and the critical current of the nanowires. According to previous studies [18,38], the critical current of our nanowires is of the order of 10 μA. The effective shunt impedance is set by the waveguide impedance of the resonator, which is R n ∼ 50 Ω.…”

Section: Fig 6 Rates Of Sps (Blue Squares) and Pps (Red Ovals) Asmentioning

confidence: 95%

Formation of Quantum Phase Slip Pairs in Superconducting Nanowires

Belkin

Vakaryuk

et al. 2015

Phys. Rev. X

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Macroscopic quantum tunneling is a fundamental phenomenon of quantum mechanics related to the actively debated topic of quantum-to-classical transition. The ability to realize macroscopic quantum tunneling affects implementation of qubit-based quantum computing schemes and their protection against decoherence. Decoherence in qubits can be reduced by means of topological protection, e.g., by exploiting various parity effects. In particular, paired phase slips can provide such protection for superconducting qubits. Here, we report on the direct observation of quantum paired phase slips in thin-wire superconducting loops. We show that in addition to conventional single phase slips that change the superconducting order parameter phase by 2π, there are quantum transitions that change the phase by 4π. Quantum paired phase slips represent a synchronized occurrence of two macroscopic quantum tunneling events, i.e., cotunneling. We demonstrate the existence of a remarkable regime in which paired phase slips are exponentially more probable than single ones. DOI: 10.1103/PhysRevX.5.021023 Subject Areas: Mesoscopics, Quantum Information, SuperconductivityDecoherence and quantum noise are primary roadblocks for large-scale implementation of quantum computing that in many cases relies on the phenomenon of macroscopic quantum tunneling [1][2][3][4][5]. Decoherence is inherently related to the collapse of macroscopic wave functions caused by various environment-induced interactions. In quantum computers, detrimental effects of decoherence can be eliminated by means of quantum error correction as originally proposed by Shor [6]. An alternative approach was suggested by Kitaev [7], who argued that the use of topologically ordered quantum systems can eliminate the burden of quantum error correction. In such systems, qubits are implemented by topologically distinct states connected by a global operation (such as braiding, in the case of anyons) that cannot be mixed by a local perturbation.Less exotic schemes of topological protection based on various parity effects in superconducting circuits have also been presented [8][9][10][11]. The crucial component of these proposals is a device that discriminates between parity-conserving and parity-violating transitions. Ideally, such a device fully suppresses the latter, thus creating well-separated parity-based sectors in the Hilbert space, which are used as a "grid" for qubit operations.Here, we focus on a multiply-connected device formed by a superconducting loop containing homogeneous superconducting nanowires. Flux states of the loop are described by the winding number (vorticity) of the superconducting phase on a path encircling the loop. Transitions between different winding number states occur through phase slips taking place in the nanowires. Realization of a parityprotected qubit requires suppression of 2π phase slips, which change the winding number by 1, and a significant amplitude of 4π phase slips, which are parity-conserving [12][13][14] events. We term them single phase s...

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Section: Fig 6 Rates Of Sps (Blue Squares) and Pps (Red Ovals) Asmentioning

confidence: 95%

Formation of Quantum Phase Slip Pairs in Superconducting Nanowires

Belkin

Vakaryuk

et al. 2015

Phys. Rev. X

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“…The assumed immediate sharing of the bias current between WL and R s implies a small inductive currentswitching time as compared to the thermal equilibration time. The minimum shunt resistor value, R sc , from our simple model can also describe the behavior of shunted nano-wire devices studied by Brenner et al [11].In this Letter, we compare the current-voltage characteristics of carefully designed WL devices with (and without) a shunt resistor kept in close vicinity of the WL, thus making the inductive current-switching time smaller than the thermal equilibration time. We observe an increase in the re-trapping current and a widening of the hysteresis-free temperature range thanks to the shunt, which we discuss using the above model.…”

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confidence: 77%

Controlling hysteresis in superconducting constrictions with a resistive shunt

Kumar¹,

Winkelmann²,

Biswas³

et al. 2015

Supercond. Sci. Technol.

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We demonstrate control of the thermal hysteresis in superconducting constrictions by adding a resistive shunt. In order to prevent thermal relaxation oscillations, the shunt resistor is placed in close vicinity of the constriction, making the inductive current-switching time smaller than the thermal equilibration time. We investigate the current-voltage characteristics of the same constriction with and without the shunt-resistor. The widening of the hysteresis-free temperature range is explained on the basis of a simple model. INTRODUCTIONA superconducting weak-link (WL), such as a constriction, between two bulk superconductors is of interest for its Josephson junction-like properties and subsequent application to micron size superconducting quantum interference devices (µ-SQUIDs) [1,2]. The latter can be used in probing magnetism at small scales [3][4][5][6]. Hysteresis present in current-voltage characteristics (IVCs) is a limiting factor in WL-based SQUIDs. In a hysteretic IVC when the current is ramped up from zero, the device typically switches to a non-zero voltage state at the critical current I c . The subsequent current ramp-down gives a switching to zero-voltage state at a smaller current, called re-trapping current I r . Hysteresis in IVCs is seen at low temperatures and disappears above a crossover temperature T h as I c and I r meet [7][8][9]. In a conventional tunnel-barrier type Josephson-junction, hysteresis arises from large junction capacitance and can be eliminated by adding a shunt-resistor in parallel to the junction [1,10]. The effect of the shunt resistor on nano-wire based WL devices was modeled recently using resistively and capacitively shunted junction (RCSJ) model with an effective capacitive time [11]. The hysteresis in similar devices is well understood using the thermal model [12]. The hysteresis in WLs is due to local Joule-heating [13,14], which gives rise to a self-sustained resistive hot-spot in the WL region, even below I c .Eliminating thermal hysteresis in WLs has been the subject of intense research in the past years. A normal metal shunt directly on top of the constriction [15][16][17] has been tried, but it affects both the superconductivity and thermal properties in a way that depends on the interface transparency. Using a bilayer with a superconductor (that can locally etched with a Focussed Ion Beam) covering a normal metal film allows one to obtain a WL that is also a good thermal bath [18]. A parallel shunt resistor far away from the WL [19] is more flexible approach, but it gives rise to relaxation oscillations due to large inductive time for switching of the current between the WL and the shunt. The performance of such SQUIDs with a distant shunt-resistor is eventually similar to that of the hysteretic ones [3,19]. A systematic study of the ability of a parallel shunt in preventing both the thermal runaway and hysteresis is thus highly desirable.The role of a shunt-resistor can be understood using a simple quasi-static thermal model discussed by Tinkham et al. [12...

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“…3,17,18 Shunting of the channel by a resistor narrows this hysteresis and, for small enough resistance, the hysteresis disappears. 18 It was suggested that shunting is able to influence the phase-slip events and hence can be used for control of dissipation and coherence in nanowires. 18 However, the dynamical mechanisms involved in the formation of the hysteresis are still not clear, and the ways that shunting drives the phase-slip events are not fully apprehended.…”

Section: Introductionmentioning

confidence: 99%

“…18 It was suggested that shunting is able to influence the phase-slip events and hence can be used for control of dissipation and coherence in nanowires. 18 However, the dynamical mechanisms involved in the formation of the hysteresis are still not clear, and the ways that shunting drives the phase-slip events are not fully apprehended. In this paper we study the dynamics of the resistive state in a narrow superconducting channel shunted by an external resistor and explore the bifurcation mechanisms involved in the hysteresis of CVCs and also responsible for the formation and evolution of PSCs.…”

Section: Introductionmentioning

confidence: 99%

Dynamics of resistive state in thin superconducting channels

2013

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We theoretically study how the dynamics of the resistive state in narrow superconducting channels shunted by an external resistor depends on channel's length L, the applied current j, and parameter u characterizing the penetration depth of the electric field in the nonequilibrium superconductors. We show that changing u dramatically affects both the behaviour of the current-voltage characteristics of the superconducting channels and the dynamics of their order parameter. Previously, it was demonstrated that when u is less than the critical value uc1, which does not depend on L, the phase slip centers appear simultaneously at different spots of the channel. Herewith, for u > uc1 these centres arise consecutively at the same place. In our work we demonstrate that there is another critical value for u. Actually, if u does not exceed a certain value uc2, which depends on L, the current-voltage characteristic exhibits the step-like behaviour. However, for u > uc2 it becomes hysteretic. In this case, with increase of j the steady state, which corresponds to the time independent distribution of the order parameter along the channel, losses its stability at switching current value jsw, and time periodic oscillations of both the order parameter and electric filed occur in the channel. As j sweeps down, the periodic dynamics ceases at certain retrapping current value jr < jsw. Shunting the channel by a resistor increases the value of jr, while jsw remains unchanged. Thus, for some high enough conductivity of the shunt jr and jsw eventually coincide, and the hysteretic loop disappears. We reveal dynamical regimes involved in the hysteresis, and discuss the bifurcation transitions between them.

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Dynamics of superconducting nanowires shunted with an external resistor

Cited by 43 publications

References 67 publications

Formation of Quantum Phase Slip Pairs in Superconducting Nanowires

Formation of Quantum Phase Slip Pairs in Superconducting Nanowires

Controlling hysteresis in superconducting constrictions with a resistive shunt

Dynamics of resistive state in thin superconducting channels

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