Exploring corrections to the optomechanical Hamiltonian

We compare two approaches for deriving corrections to the “linear model” of cavity optomechanics, in order to describe effects that are beyond first order in the radiation pressure coupling. In the regime where the mechanical frequency is much lower than the cavity one, we compare: (I) a widely used phenomenological Hamiltonian conserving the photon number; (II) a two-mode truncation of C. K. Law’s microscopic model, which we take as the “true” system Hamiltonian. While these approaches agree at first order, the latter model does not conserve the photon number, resulting in challenging computations. We find that approach (I) allows for several analytical predictions, and significantly outperforms the linear model in our numerical examples. Yet, we also find that the phenomenological Hamiltonian cannot fully capture all high-order corrections arising from the C. K. Law model

Nano-Opto-Electro-Mechanical Systems

A new class of hybrid systems that couple optical, electrical and mechanical degrees of freedom in nanoscale devices is under development in laboratories worldwide. These nano-opto-electro-mechanical systems (NOEMS) offer unprecedented opportunities to dynamically control the flow of light in nanophotonic structures, at high speed and low power consumption. Drawing on conceptual and technological advances from cavity optomechanics, they also bear the potential for highly efficient, low-noise transducers between microwave and optical signals, both in the classical and quantum domains. This Progress Article discusses the fundamental physical limits of NOEMS, reviews the recent progress in their implementation, and suggests potential avenues for further developments in this field.Comment: 27 pages, 3 figures, 2 boxe

State Preparation and Tomography of a Nanomechanical Resonator with Fast Light Pulses

Pulsed optomechanical measurements enable squeezing, nonclassical state creation, and backaction-free sensing. We demonstrate pulsed measurement of a cryogenic nanomechanical resonator with record precision close to the quantum regime. We use these to prepare thermally squeezed and purified conditional mechanical states, and to perform full state tomography. These demonstrations exploit large vacuum optomechanical coupling in a nanophotonic cavity to reach a single-pulse imprecision of 9 times the mechanical zero-point amplitude xzpf. We study the effect of other mechanical modes that limit the conditional state width to 58xzpf, and show how decoherence causes the state to grow in time.peerReviewe

Regulation of average 24h human plasma leptin level; the influence of exercise and physiological changes in energy balance.

OBJECTIVE: The effects of short-term moderate physiological changes in energy flux and energy balance, by exercise and over- or underfeeding, on a 24h plasma leptin profile, were investigated. DESIGN: Subjects were studied over 24h in four randomized conditions: no exercise/energy balance (energy intake (EI)=energy expenditure (EE)=11.8+/-0.8 MJ); exercise/energy balance (EI=EE=15.1+/-0.6 MJ); exercise/negative energy balance (EI=11.8+/-0.8 MJ, EE=15.1+/-0.8 MJ); exercise/positive energy balance (El=18.6+/-0.7 MJ, EE=15.1+/-0.6 MJ). SUBJECTS: Eight healthy, lean men (age: 23.5+/-7.0y, body fat 14.1+/-5.4%, body mass index (BMI): 21.4+/-2.3 kg/m2). MEASUREMENTS: Blood was sampled every hour during the daytime (09.00-23.00h) and every two hours during the night (01.00-09.00h) for analysis of plasma leptin, insulin, glucose, FFA and catecholamines. RESULTS: Plasma leptin levels were highest around 01.00h (mean+/-s.e.m. 4.9+/-2.0 ng/ml) and lowest around 11.00 h. (2.3+/-0.7 ng/ml). An increased 24h EE, induced by exercise under conditions of energy balance, significantly decreased the peak and average 24h plasma leptin concentration. A positive energy balance, by overfeeding, resulted in a significantly higher amplitude of the 24h plasma leptin curve, compared to a condition of energy balance. CONCLUSION: Exercise decreases peak and average 24h plasma leptin concentration and a moderately positive energy balance increases the amplitude of the 24h plasma leptin profile. These effects are not acute, but are manifest within 24h. The variations of average 24h FFA and average 24h glucose concentrations almost fully explained the variation in average 24h leptin concentration across trials

Quadrature-Averaged Homodyne Detection for Estimating Cavity Parameters

Balanced homodyne interferometry is a well-known detection technique that allows for sensitive characterization of light fields. Conventionally a homodyne interferometer is operated by locking the relative phase of a reference beam to the signal beam by means of an active feedback loop. A less often used method is to perform a slow continuous modulation of the reference beam arm length that corresponds to averaging all relative phases during the measurement. Here we show theoretically and experimentally that this quadrature averaging can be advantageous in estimating the parameters of a resonant optical cavity. We demonstrate that the averaging turns the transduction function, from cavity frequency fluctuations into the interferometer signal, into a simple function of the laser detuning that, notably, does not depend on the parameters of possible nonresonant channels present in the system. The method needs no active feedback and gives results that are easy to interpret. Moreover, the phase-averaged measurement allows characterization of the absolute magnitude of a cavity frequency modulation.peerReviewe