Glen I. Harris

Cooling and Control of a Cavity Optoelectromechanical System

We implement a cavity optoelectromechanical system integrating electrical actuation capabilities of nanoelectromechanical devices with ultrasensitive mechanical transduction achieved via intracavity optomechanical coupling. Electrical gradient forces as large as 0.40 microN are realized, with simultaneous mechanical transduction sensitivity of 1.5x10{-18} m Hz{-1/2} representing a 3 orders of magnitude improvement over any nanoelectromechanical system to date. Optoelectromechanical feedback cooling is demonstrated, exhibiting strong squashing of the in-loop transduction signal. Out-of-loop transduction provides accurate temperature calibration even in the critical paradigm where measurement backaction induces optomechanical correlations.

Mechanical squeezing via parametric amplification and weak measurement

Nonlinear forces allow motion of a mechanical oscillator to be squeezed below the zero-point motion. Of existing methods, mechanical parametric amplification is relatively accessible, but previously thought to be limited to 3 dB of squeezing in the steady state. We consider the effect of applying continuous weak measurement and feedback to this system. If the parametric drive is optimally detuned from resonance, correlations between the quadratures of motion allow unlimited steady-state squeezing. Compared to backaction evasion, we demonstrate that the measurement strength, temperature and efficiency requirements for quantum squeezing are significantly relaxed.

Quantum-enhanced micromechanical displacement sensitivity

We report on a hitherto unexplored application of squeezed light: for quantum-enhancement of mechanical transduction sensitivity in microcavity optomechanics. Using a toroidal silica microcavity, we experimentally demonstrate measurement of the transduced phase modulation signal in the frequency range 4-5.8 MHz with a sensitivity -0.72(±0.01) dB below the shot noise level. This is achieved for resonant probing in the highly undercoupled regime, by preparing the probe in a weak coherent state with phase squeezed vacuum states at sideband frequencies.

Laser cooling and control of excitations in superfluid helium

It takes extreme sensitivity to measure the elementary excitations in liquid helium-4. An optomechanical cavity with a thin film of superfluid inside can be used to both observe and control phonons in real time.

Minimum requirements for feedback enhanced force sensing

The paper theoretically shows that for linear oscillators neither stationary nor non-stationary linear feedback provide any sensitivity enhancement over that possible with estimation alone. Importantly this result holds true in both the quantum and classical regime and in the presence of non-Gaussian noise terms. It is experimentally demonstrated that detection of a small stationary incoherent force can be enhanced by estimation in the same way as feedback cooling. The system presented is a cavity opto-electromechanical system (COEMS) consisting of an evanescently coupled silica microtoroid integrating high Q mechanical and optical modes. The incoherent signal, which is uncorrelated to the thermal noise, was applied via an electrode which facilitated strong electrical actuation through strong electrical gradient forces. The effect of the incoherent force on the mechanics manifests as an increase in the temperature of the mechanical oscillator. Energy averaging is used to resolve the temperature discrepancies and detect the signal. Enabling force sensitivity through post-processing without the need for feedback techniques greatly simplifies the role of micromechanical oscillators in sensing applications and fundamental research.

Feedback-enhanced sensitivity in optomechanics: Surpassing the parametric instability barrier

The intracavity power, and hence sensitivity, of optomechanical sensors is commonly limited by parametric instability. Here we characterize the degradation of sensitivity induced by parametric instability in a micron-scale cavity optomechanical system. Feedback via optomechanical transduction and electrical gradient force actuation is applied to suppress the parametric instability. As a result a 5.4-fold increase in mechanical motion transduction sensitivity is achieved to a final value of 1.9 x 10(-18) mHz(-1/2).

Cavity optoelectromechanical system combining strong electrical actuation with ultrasensitive transduction

A cavity optoelectromechanical system is reported which combines the ultrasensitive transduction of cavity optomechanical systems with the electrical actuation of nanoelectromechanical systems. Ultrasensitive mechanical transduction is achieved via optomechanical coupling. Electrical gradient forces as large as

Quantum enhanced feedback cooling of a mechanical oscillator using nonclassical light

0.40

The quantum trajectory approach to quantum feedback control of an oscillator revisited.

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