Homodyne detection of matter-wave fields

TL;DR

This paper proposes a homodyne detection scheme for matter-wave fields in ultracold bosonic atoms using a pump-probe laser setup, enabling phase-sensitive measurements and quantum state analysis.

Contribution

It introduces a novel method to perform homodyne detection of matter-wave fields, leveraging atom-photon entanglement for detailed quantum state characterization.

Findings

Demonstrates oscillations in atom flux and photon scattering related to condensate fraction.

Enables thermometry and phase transition monitoring in ultracold gases.

Provides a technique to measure the first-order correlation function of quantum gases.

Abstract

A scheme is proposed, that allows one for performing homodyne detection of the matter-wave field of ultracold bosonic atoms. It is based on a pump-probe lasers setup, that both illuminates a Bose-Einstein condensate, acting as reference system, and a second ultracold gas, composed by the same atoms but in a quantum phase to determine. Photon scattering outcouples atoms from both systems, which then propagate freely. Under appropriate conditions, when the same photon can either be scattered by the Bose-Einstein condensate or by the other quantum gas, both flux of outcoupled atoms and scattered photons exhibit oscillations, whose amplitude is proportional to the condensate fraction of the quantum gas. This setup allows one, for instance, to perform thermometry of a condensate or to monitor the Mott-insulator/superfluid phase transition in optical lattices, and can be extended in order to measure the first-order correlation function of a quantum gas. The dynamics here discussed make use of the entanglement between atoms and photons, which is established by the scattering process, in order to access detailed information on the quantum state of matter.