Imaging Correlations in Heterodyne Spectra for Quantum Displacement Sensing

A. Pontin, J.E. Lang, A. Chowdhury, P. Vezio, F. Marino, Bruno Morana, Enrico Serra, F. Marin, T.S. Monteiro

Research output: Contribution to journalArticleScientificpeer-review

13 Citations (Scopus)
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The extraordinary sensitivity of the output field of an optical cavity to small quantum-scale displacements has led to breakthroughs such as the first detection of gravitational waves and of the motions of quantum ground-state cooled mechanical oscillators. While heterodyne detection of the output optical field of an optomechanical system exhibits asymmetries which provide a key signature that the mechanical oscillator has attained the quantum regime, important quantum correlations are lost. In turn, homodyning can detect quantum squeezing in an optical quadrature but loses the important sideband asymmetries. Here we introduce and experimentally demonstrate a new technique, subjecting the autocorrelators of the output current to filter functions, which restores the lost heterodyne correlations (whether classical or quantum), drastically augmenting the useful information accessible. The filtering even adjusts for moderate errors in the locking phase of the local oscillator. Hence we demonstrate the single-shot measurement of hundreds of different field quadratures allowing the rapid imaging of detailed features from a simple heterodyne trace. We also obtain a spectrum of hybrid homodyne-heterodyne character, with motional sidebands of combined amplitudes comparable to homodyne. Although investigated here in a thermal regime, the method's robustness and generality represents a promising new approach to sensing of quantum-scale displacements.

Original languageEnglish
Article number020503
Pages (from-to)1-6
Number of pages6
JournalPhysical Review Letters
Issue number2
Publication statusPublished - 2018


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