Entanglement-Enhanced Matter-Wave Interferometry in a High-Finesse Cavity

TL;DR

This paper demonstrates entanglement-enhanced matter-wave interferometry with 700 atoms in a cavity-QED system, achieving measurement precision surpassing the standard quantum limit and opening new avenues for quantum sensing and fundamental physics.

Contribution

The work introduces the first successful injection of entangled states into a matter-wave interferometer, achieving direct metrological enhancement beyond the standard quantum limit.

Findings

Achieved 3.4 dB metrological gain with quantum non-demolition measurements.

Achieved 2.5 dB metrological gain with cavity-mediated spin interactions.

Injected entangled states into a Mach-Zehnder interferometer with 1.7 dB enhancement.

Abstract

Entanglement is a fundamental resource that allows quantum sensors to surpass the standard quantum limit set by the quantum collapse of independent atoms. Collective cavity-QED systems have succeeded in generating large amounts of directly observed entanglement involving the internal degrees of freedom of laser-cooled atomic ensembles. Here we demonstrate cavity-QED entanglement of external degrees of freedom to realize a matter-wave interferometer of 700 atoms in which each individual atom falls freely under gravity and simultaneously traverses two paths through space while also entangled with the other atoms. We demonstrate both quantum non-demolition measurements and cavity-mediated spin interactions for generating squeezed momentum states with directly observed metrological gain $3.4^{+1.1}_{-0.9}$ dB and $2.5^{+0.6}_{-0.6}$ dB below the standard quantum limit respectively. An entangled state is for the first time successfully injected into a Mach-Zehnder light-pulse interferometer with $1.7^{+0.5}_{-0.5}$ dB of directly observed metrological enhancement. Reducing the fundamental quantum source of imprecision provides a new resource that can be exploited to directly enhance measurement precision, bandwidth, and accuracy or operate at reduced size. These results also open a new path for combining particle delocalization and entanglement for inertial sensors, searches for new physics, particles, and fields, future advanced gravitational wave detectors, and accessing beyond mean-field quantum many-body physics.