Appearance and Disappearance of Quantum Correlations in Measurement-Based Feedback Control of a Mechanical Oscillator

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 i...

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Bibliographic Details
Published in:Physical review. X 2017-01, Vol.7 (1), p.011001, Article 011001
Main Authors: Sudhir, V., Wilson, D. J., Schilling, R., Schütz, H., Fedorov, S. A., Ghadimi, A. H., Nunnenkamp, A., Kippenberg, T. J.
Format: Article
Language:English
Subjects:
Amplitudes
Asymmetry
Compressing
Control systems
Control theory
Cryogenic temperature
Feedback control
Feedback loops
Frequency shift
Lasers
Mechanical oscillators
Mechanical systems
Photoelectric effect
Photoelectric emission
Position measurement
Quadratures
Quantum mechanics
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Summary: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.
ISSN:2160-3308
2160-3308
DOI:10.1103/PhysRevX.7.011001