Phase-slip flux qubits

TL;DR

This paper proposes using quantum phase-slip in thin superconducting wires to create a new type of superconducting qubit, potentially avoiding the need for Josephson junctions and enabling coherent quantum states.

Contribution

It introduces a novel qubit design based on quantum phase-slip in nanowires, expanding the possibilities for superconducting quantum computing architectures.

Findings

Quantum phase-slip can coherently couple macroscopic current states.

A specific niobium-silicon nanowire design is proposed for experimental realization.

The approach offers an alternative to Josephson junction-based qubits.

Abstract

In thin superconducting wires, phase-slip by thermal activation near the critical temperature is a well-known effect. It has recently become clear that phase-slip by quantum tunnelling through the energy barrier can also have a significant rate at low temperatures. In this paper it is suggested that quantum phase-slip can be used to realize a superconducting quantum bit without Josephson junctions. A loop containing a nanofabricated very thin wire is biased with an externally applied magnetic flux of half a flux quantum, resulting in two states with opposite circulating current and equal energy. Quantum phase-slip should provide coherent coupling between these two macroscopic states. Numbers are given for a wire of amorphous niobium-silicon that can be fabricated with advanced electron beam lithography.