Matters Arising: Entanglement-enhanced matter-wave interferometry in a high-finesse cavity

TL;DR

The paper critically examines a 2022 study claiming entanglement-enhanced matter-wave interferometry surpassing the standard quantum limit, and finds the original claims to be incorrect due to measurement errors and overestimations.

Contribution

It provides a detailed critique of the original experiment, clarifying that the claimed sensitivity improvements were not achieved and highlighting the importance of accurate data interpretation.

Findings

Original claims of surpassing SQL are incorrect

Measured sensitivity was significantly worse than claimed

Highlights the need for rigorous validation in quantum metrology

Abstract

In their paper "Entanglement-enhanced matter-wave interferometry in a high-finesse cavity" Nature (2022), Greve et. al. claim to use entanglement in a matter-wave interferometer to achieve a sensitivity beyond that achievable with the same number of independent particles -- a limit known as the standard quantum limit (SQL). In particular, using squeezed momentum states of 700 atoms, the authors claim to directly observe a sensitivity 3.4 dB (a factor of 1.5) below the SQL. This claim is incorrect. The authors do not measure anything beyond the SQL, nor do they achieve a sensitivity beyond what one could obtain with a single atom. The achieved sensitivity is at least a factor of 39 worse than the claimed value.