Strong parametric squeezing of thermal motion in a micromagnetomechanical system

Seminar

Parametric excitation of a resonator at twice the resonance frequency is conceptually the simplest way to produce squeezing and amplification of the resonator quadratures. Classical parametric squeezing of thermal motion in a micromechanical resonator was demonstrated by Rugar and Grutter long time ago [1]. Unfortunately, the onset of instability in the amplified quadrature limits the maximum achievable squeezing to only 3 dB. Here, I will show that it is possible to considerably increase the stationary squeezing factor by means of single-quadrature feedback control of the amplified quadrature. The scheme has been demonstrated in a cryogenic micromagnetomechanical system [2], composed by a magnetically tipped ultrasoft cantilever strongly coupled to a dc SQUID. This experimental setup was primarily developed in the framework of Magnetic Resonance Force Microscopy experiments. The proposed squeezing scheme can be in principle implemented in any kind of mechanical resonator regardless of the specific detection technique, provided that a sufficiently strong parametric modulation is available. The maximum stationary parametric squeezing achieved in the present experiment is a factor 100, corresponding to 20 dB. Starting from a sufficiently low thermal occupation number, it should be possible to use this scheme to achieve quantum squeezing of a mechanical quadrature. It is acknowledged the support of European Commission (Marie Curie Action COFUND - Grant agreement No. 267224). [1] D. Rugar and P. Grutter, “Mechanical parametric amplification and thermomechanical noise squeezing”, Phys. Rev. Lett. 67, 699 (1991). [2] A. Vinante and P. Falferi, “Feedback-enhanced parametric squeezing of mechanical motion”, Phys. Rev. Lett. 111, 207203 (2013).

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