Mesoscopic atomic entanglement for precision measurements beyond the standard quantum limit

TL;DR

This paper demonstrates significant entanglement and squeezing in cold cesium atoms using a two-color quantum nondemolition measurement, enhancing precision in quantum sensing beyond standard limits.

Contribution

It introduces a two-color QND scheme that optimizes entanglement generation and surpasses previous methods in atomic squeezing for quantum metrology.

Findings

Achieved 3.4 dB of metrologically relevant squeezing.

Demonstrated entanglement in approximately 10^5 cesium atoms.

Identified optimal decoherence level for maximum entanglement.

Abstract

Squeezing of quantum fluctuations by means of entanglement is a well recognized goal in the field of quantum information science and precision measurements. In particular, squeezing the fluctuations via entanglement between two-level atoms can improve the precision of sensing, clocks, metrology, and spectroscopy. Here, we demonstrate 3.4 dB of metrologically relevant squeezing and entanglement for ~ 10^5 cold cesium atoms via a quantum nondemolition (QND) measurement on the atom clock levels. We show that there is an optimal degree of decoherence induced by the quantum measurement which maximizes the generated entanglement. A two-color QND scheme used in this paper is shown to have a number of advantages for entanglement generation as compared to a single color QND measurement.