arXiv:2509.13810

Loss-tolerant detection of squeezed states in the 2 um region

K. M. Kwan, T. McRae, Jiayi Qin, D.W Gould, S. Chua, J. Junker, R. Iden, V. B. Adya, M. J. Yap, Bram J. J. Slagmolen, David E. McClelland, Robert L. Ward

Published Sep 17, 2025• 0 citations

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Abstract

Squeezed states of light enable quantum-enhanced measurements but are limited by optical loss, particularly at 2 um where photodiode efficiency is low. We report the first loss-tolerant, audio-band squeezed light detection at 1984 nm by using a phase-sensitive amplifier to amplify the squeezed vacuum prior to detection. This technique increases the effective detection efficiency from 74% to 95% and increases the observed squeezing from 4 dB to 8 dB, the highest level of squeezing observed at this wavelength. Additionally, the shot-to-dark-noise clearance increases, extending the effective measurement bandwidth toward lower frequencies. This approach is largely wavelength-independent, extending high-fidelity quantum measurements to future gravitational-wave detectors and related quantum technologies.

DOI: 10.48550/arxiv.2509.13810

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