Matters Arising: Distributed quantum sensing with mode-entangled spin-squeezed atomic states

TL;DR

This paper critically examines a recent claim of enhanced precision in distributed quantum sensing using entangled atomic states, revealing that the reported improvements are significantly below the quantum noise limit and thus not valid.

Contribution

The authors provide a detailed analysis showing that the previous experimental results do not surpass the quantum projection noise limit, correcting the misinterpretation of the original claims.

Findings

The claimed precision improvement is overestimated by more than two orders of magnitude.

The actual experimental performance is far below the quantum projection noise limit.

The paper clarifies the correct interpretation of quantum sensing limits in the context of the original experiment.

Abstract

In ``Distributed quantum sensing with mode-entangled spin-squeezed atomic states" Nature (2022), Malia et. al. claim to improve the precision of a network of clocks by using entanglement. In particular, by entangling a clock network with up to four nodes, a precision 11.6 dB better than the quantum projection noise limit (i.e. precision without any entanglement) is reported. These claims are incorrect, Malia et. al. do not achieve an improved precision with entanglement. Here we show their demonstration is more than two orders of magnitude worse than the quantum projection noise limit.