Coherent superposition of current flows in an Atomtronic Quantum Interference Device

TL;DR

This paper investigates a Bose gas in a ring lattice with a weak link, demonstrating how it can function as a quantum interference device (AQUID) by forming a coherent superposition of current states, useful for atomic qubits.

Contribution

It shows how to realize and analyze an atomic quantum interference device using a correlated Bose gas, highlighting conditions for effective qubit operation.

Findings

Effective two-level system emerges in the setup.

Superposition of current states visible in momentum distribution.

Intermediate-to-strong interactions with weak barriers optimize qubit properties.

Abstract

We consider a correlated Bose gas tightly confined into a ring shaped lattice, in the presence of an artificial gauge potential inducing a persistent current through it. A weak link painted on the ring acts as a source of coherent back-scattering for the propagating gas, interfering with the forward scattered current. This system defines an atomic counterpart of the rf-SQUID: the atomtronics quantum interference device (AQUID). The goal of the present study is to corroborate the emergence of an effective two-level system in such a setup and to assess its quality, in terms of its inner resolution and its separation from the rest of the many-body spectrum, across the different physical regimes. In order to achieve this aim, we examine the dependence of the qubit energy gap on the bosonic density, the interaction strength, and the barrier depth, and we show how the superposition between current states appears in the momentum distribution (time-of-flight) images. A mesoscopic ring lattice with intermediate-to-strong interactions and weak barrier depth is found to be a favorable candidate for setting up, manipulating and probing a qubit in the next generation of atomic experiments.