Overcoming detection loss and noise in squeezing-based optical sensing

TL;DR

This paper demonstrates a method to counteract loss and noise in squeezing-based optical sensing using noiseless amplification, enabling quantum-enhanced measurements even under high loss and noise conditions.

Contribution

The authors experimentally show that noiseless amplification can make squeezing-based sensing loss-tolerant, extending the practical applicability of quantum metrology in noisy environments.

Findings

Achieved 6 dB loss-tolerant sub-shot-noise sensitivity with 50% detection efficiency.

Maintained sub-shot-noise phase sensitivity up to 87% loss.

Demonstrated robustness against noise exceeding squeezed light levels by over 50 times.

Abstract

Among the known resources of quantum metrology, one of the most practical and efficient is squeezing. Squeezed states of atoms and light improve the sensing of the phase, magnetic field, polarization, mechanical displacement. They promise to considerably increase signal-to-noise ratio in imaging and spectroscopy, and are already used in real-life gravitational-wave detectors. But despite being more robust than other states, they are still very fragile, which narrows the scope of their application. In particular, squeezed states are useless in measurements where the detection is inefficient or the noise is high. Here, we experimentally demonstrate a remedy against loss and noise: strong noiseless amplification before detection. This way, we achieve loss-tolerant operation of an interferometer fed with squeezed and coherent light. With only 50\% detection efficiency and with noise exceeding the level of squeezed light more than 50 times, we overcome the shot-noise limit by 6~dB. Sub-shot-noise phase sensitivity survives up to 87\% loss. Application of this technique to other types of optical sensing and imaging promises a full use of quantum resources in these fields.