Appearance and disappearance of quantum correlations in measurement-based feedback control of a mechanical oscillator

Sudhir, Vivishek; Wilson, Dalziel J; Schilling, Ryan; Sch�tz, Hendrik; Fedorov, Sergey A; Ghadimi, Amir H; Nunnenkamp, Andreas; Kippenberg, Tobias J

Abstract

Quantum correlations between imprecision and backaction are a hallmark of continuous linear measurements. Here, we study how measurement-based feedback can be used to improve the visibility of quantum correlations due to the interaction of a laser field with a nanomechanical oscillator. Backaction imparted by the meter laser, due to radiation-pressure quantum fluctuations, gives rise to correlations between its phase and amplitude quadratures. These quantum correlations are observed in the experiment both as squeezing of the meter field fluctuations below the vacuum level in a homodyne measurement and as sideband asymmetry in a heterodyne measurement, demonstrating the common origin of both phenomena. We show that quantum feedback, i.e., feedback that suppresses measurement backaction, can be used to increase the visibility of the sideband asymmetry ratio. In contrast, by operating the feedback loop in the regime of noise squashing, where the in-loop photocurrent variance is reduced below the vacuum level, the visibility of the sideband asymmetry is reduced. This is due to backaction arising from vacuum noise in the homodyne detector. These experiments demonstrate the possibility, as well as the fundamental limits, of measurement-based feedback as a tool to manipulate quantum correlations.

• Journal Article Type: Article
• Acceptance Date: Nov 18, 2016
• Online Publication Date: Jan 6, 2017
• Publication Date: 2017-01
• Deposit Date: Jul 14, 2020
• Publicly Available Date: Jul 16, 2020
• Journal: Physical Review X
• Electronic ISSN: 2160-3308
• Publisher: American Physical Society
• Peer Reviewed: Peer Reviewed
• Volume: 7
• Issue: 1
• Article Number: 011001
• DOI: https://doi.org/10.1103/PhysRevX.7.011001
• Keywords: General Physics and Astronomy
• Public URL: https://nottingham-repository.worktribe.com/output/4765588
• Publisher URL: https://journals.aps.org/prx/abstract/10.1103/PhysRevX.7.011001