Overcoming detection loss and noise in squeezing-based optical sensing

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