Readout of the atomtronic quantum interference device

TL;DR

This paper demonstrates a method to detect current states in an atomtronic quantum interference device using a self-heterodyne protocol, analyzing interference patterns and noise to distinguish quantum coherence states.

Contribution

It introduces a self-heterodyne detection protocol for AQUIDs, applicable to Bose-Hubbard and Gross-Pitaevskii models, for reading out current states and quantum coherence.

Findings

Self-heterodyne protocol can detect current states in AQUIDs.

Higher-order correlations are essential for reading out quantum states.

Noise analysis in time of flight reveals macroscopic quantum coherence.

Abstract

A Bose-Einstein condensate confined in ring shaped lattices interrupted by a weak link and pierced by an effective magnetic flux defines the atomic counterpart of the superconducting quantum interference device: the atomtronic quantum interference device (AQUID). In this paper, we report on the detection of current states in the system through a self-heterodyne protocol. Following the original proposal of the NIST and Paris groups, the ring-condensate many-body wave function interferes with a reference condensate expanding from the center of the ring. We focus on the rf-AQUID which realizes effective qubit dynamics. Both the Bose-Hubbard and Gross-Pitaevskii dynamics are studied. For the Bose-Hubbard dynamics, we demonstrate that the self-heterodyne protocol can be applied, but higher-order correlations in the evolution of the interfering condensates are measured to readout of the current states of the system. We study how states with macroscopic quantum coherence can be told apart analyzing the noise in the time of flight of the ring condensate.