Appearance and Disappearance of Quantum Correlations in Measurement-Based Feedback Control of a Mechanical Oscillator
Physical Review X
American Physical Society
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Sudhir, V., Wilson, D., Schilling, R., Schuetz, H., Fedorov, S., Ghadimi, A., Nunnenkamp, A., & et al. (2017). Appearance and Disappearance of Quantum Correlations in Measurement-Based Feedback Control of a Mechanical Oscillator. Physical Review X, 7 (1. 011001), 1-14. https://doi.org/10.1103/PhysRevX.7.011001
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.
Research is funded by an ERC Advanced Grant (QuREM), a Marie Curie Initial Training Network Cavity Quantum Optomechanics, the Swiss National Science Foundation, and through support from the NCCR of Quantum Engineering (QSIT). D. J. W. acknowledges support from the European Commission through a Marie Curie Fellowship (IIF Project No. 331985).
Royal Society (uf130303)
External DOI: https://doi.org/10.1103/PhysRevX.7.011001
This record's URL: https://www.repository.cam.ac.uk/handle/1810/262474
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