Preliminary demonstration of a persistent Josephson phase-slip memory cell with topological protection

Nadia Ligato,Francesco Giazotto,Federico Paolucci,Elia Strambini

doi:10.1038/s41467-021-25209-y

Nadia Ligato, Francesco Giazotto + Show 2 more

Open Access

https://doi.org/10.1038/s41467-021-25209-y

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Abstract

Superconducting computing promises enhanced computational power in both classical and quantum approaches. Yet, scalable and fast superconducting memories are not implemented. Here, we propose a fully superconducting memory cell based on the hysteretic phase-slip transition existing in long aluminum nanowire Josephson junctions. Embraced by a superconducting ring, the memory cell codifies the logic state in the direction of the circulating persistent current, as commonly defined in flux-based superconducting memories. But, unlike the latter, the hysteresis here is a consequence of the phase-slip occurring in the long weak link and associated to the topological transition of its superconducting gap. This disentangles our memory scheme from the large-inductance constraint, thus enabling its miniaturization. Moreover, the strong activation energy for phase-slip nucleation provides a robust topological protection against stochastic phase-slips and magnetic-flux noise. These properties make the Josephson phase-slip memory a promising solution for advanced superconducting classical logic architectures or flux qubits.

Highlights

Superconducting computing promises enhanced computational power in both classical and quantum approaches
The design of a proof-ofconcept phase-slip memory (PSM) requires an architecture enabling the tuning of the superconducting phase and the definition of an efficient readout scheme
The Josephson junction (JJ) is inserted in a superconducting loop, where an external magnetic field gives rise to a total flux (Φ) piercing the ring area

Summary

Introduction

Superconducting computing promises enhanced computational power in both classical and quantum approaches. Embraced by a superconducting ring, the memory cell codifies the logic state in the direction of the circulating persistent current, as commonly defined in flux-based superconducting memories Unlike the latter, the hysteresis here is a consequence of the phase-slip occurring in the long weak link and associated to the topological transition of its superconducting gap. In a fully superconducting one-dimensional JJ (w, t ≪ ξw) the CPR evolves from the single-valued distorted sinusoidal characteristic, typical of the short-junction limit (L ≪ ξw Fig. 1a) and of nonsuperconducting weak links, to the multi-valued function obtained in the long regime (L ≫ ξw, Fig. 1b)[2] In the latter scenario, multiple (odd) solutions are available to the system at fixed φ, and the steady state will depend on the history of φ.

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