Abstract

Cavity opto-mechanics has recently achieved major experimental breakthroughs, such as optical cooling of opto-mechanical oscillators down to a thermal occupation number around or below unity, the consequent observation of quantum signatures in the spectrum of a macroscopic mechanical oscillator, strongly coupled states of radiation and mechanical oscillations. A great deal of attention is now devoted to possible realizations of strongly non-classical states of macroscopic variables, that would open the way to new quantum information tools, as well as to crucial tests on the classical-to-quantum transition. In this framework, several techniques to obtain squeezed of the motion quadratures have been studied and demonstrated on thermal oscillators, including quantum non-demolition measurements and parametric excitation. Concerning the last subject, its basic application in a stationary system just allows an uncertainty reduction in one quadrature to -3dB below the vacuum fluctuations, limited by the burst of parametric oscillations in the conjugate quadrature. We have recently reported the confinement of an optomechanical micro-oscillator in a squeezed thermal state, obtained by parametric modulation of the optical spring [1]. Thanks to a parametric feedback control of the oscillator, which stabilizes the amplified quadrature while leaving the orthogonal one unaffected [2], we could surpass the -3dB barrier, with a best experimental result of −7.4dB.

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