Anyonic interferometry without anyons: How a flux qubit can read out a topological qubit

TL;DR

This paper proposes a method using a flux qubit in a Josephson junction circuit to read out topological qubits encoded in anyons without requiring anyons to be physically present, overcoming previous limitations.

Contribution

It introduces a novel interferometry scheme employing coreless Josephson vortices and flux qubits to nondestructively measure topological qubits, avoiding the need for anyons to be directly involved.

Findings

Demonstrates that flux qubits can read out topological qubits without anyons.

Shows that coreless Josephson vortices enable quantum interference without classical vortex dynamics.

Removes temperature restrictions on anyonic interferometry in superconductors.

Abstract

Proposals to measure non-Abelian anyons in a superconductor by quantum interference of vortices suffer from the predominantly classical dynamics of the normal core of an Abrikosov vortex. We show how to avoid this obstruction using coreless Josephson vortices, for which the quantum dynamics has been demonstrated experimentally. The interferometer is a flux qubit in a Josephson junction circuit, which can nondestructively read out a topological qubit stored in a pair of anyons --- even though the Josephson vortices themselves are not anyons. The flux qubit does not couple to intra-vortex excitations, thereby removing the dominant restriction on the operating temperature of anyonic interferometry in superconductors.