Quantum Correlations of Light from a Room-Temperature Mechanical Oscillator

• Published in: Physical review. X Vol. 7; no. 3; p. 031055
• Main Authors: Sudhir, V., Schilling, R., Fedorov, S. A., Schütz, H., Wilson, D. J., Kippenberg, T. J.
• Format: Journal Article
• Language: English
• Published: College Park American Physical Society 26.09.2017
• Subjects: Accelerometers; Ambient temperature; Broadband; Distillation; Electromagnetic radiation; Force measurement; Gravitational waves; Light; Mechanical oscillators; Noise; Position measurement; Pressure effects; Quadratures; Quantum mechanics; Radiation; Radiation pressure; Resonance; Room temperature; Signal to noise ratio; Squeezed states (quantum theory); Vacuum chambers; Whispering gallery modes
• ISSN: 2160-3308; 2160-3308
• DOI: 10.1103/PhysRevX.7.031055

When an optical field is reflected from a compliant mirror, its intensity and phase become quantum-correlated due to radiation pressure. These correlations form a valuable resource: the mirror may be viewed as an effective Kerr medium generating squeezed states of light, or the correlations may be used to erase backaction from an interferometric measurement of the mirror’s position. To date, optomechanical quantum correlations have been observed in only a handful of cryogenic experiments, owing to the challenge of distilling them from thermomechanical noise. Accessing them at room temperature, however, would significantly extend their practical impact, with applications ranging from gravitational wave detection to chip-scale accelerometry. Here, we observe broadband quantum correlations developed in an optical field due to its interaction with a room-temperature nanomechanical oscillator, taking advantage of its high-cooperativity near-field coupling to an optical microcavity. The correlations manifest as a reduction in the fluctuations of a rotated quadrature of the field, in a frequency window spanning more than an octave below mechanical resonance. This is due to coherent cancellation of the two sources of quantum noise contaminating the measured quadrature—backaction and imprecision. Supplanting the backaction force with an off-resonant test force, we demonstrate the working principle behind a quantum-enhanced “variational” force measurement.