Homodyne Measurements on a Bose-Einstein Condensate

TL;DR

This paper presents a non-destructive homodyne measurement method to monitor Josephson-like oscillations in a Bose-Einstein condensate system, revealing measurement-induced phase dynamics and oscillations.

Contribution

It introduces a novel measurement technique using cavity homodyne detection to observe condensate oscillations without destroying the system.

Findings

Detection of Josephson-like oscillations via cavity output

Measurement back-action induces phase and oscillations

Dispersive phase shift correlates with atom number

Abstract

We investigate a non-destructive measurement technique to monitor Josephson-like oscillations between two spatially separated neutral atom Bose-Einstein condensates. One condensate is placed in an optical cavity, which is strongly driven by a coherent optical field. The cavity output field is monitored using a homodyne detection scheme. The cavity field is well detuned from an atomic resonance, and experiences a dispersive phase shift proportional to the number of atoms in the cavity. The detected current is modulated by the coherent tunneling oscillations of the condensate. Even when there is an equal number of atoms in each well initially, a phase is established by the measurement process and Josephson-like oscillations develop due to measurement back-action noise alone.