Quantum Optomechanics Research Articles

Pulsed Laser Cooling for Cavity Optomechanical Resonators

A pulsed cooling scheme for optomechanical systems is presented that is capable of cooling at much faster rates, shorter overall cooling times, and for a wider set of experimental scenarios than is possible by conventional methods. The proposed scheme can be implemented for both strongly and weakly coupled optomechanical systems in both weakly and highly dissipative cavities. We study analytically its underlying working mechanism, which is based on interferometric control of optomechanical interactions, and we demonstrate its efficiency with pulse sequences that are obtained by using methods from optimal control. The short time in which our scheme approaches the optomechanical ground state allows for a significant relaxation of current experimental constraints. Finally, the framework presented here can be used to create a rich variety of optomechanical interactions and hence offers a novel, readily available toolbox for fast optomechanical quantum control.

High-sensitivity three-mode optomechanical transducer

Three-mode optomechanical interactions have been predicted to allow the creation of very high sensitivity transducers in which very strong optical self-cooling and strong optomechanical quantum entanglement are predicted. Strong coupling is achieved by engineering a transducer in which both the pump laser and a single signal sideband frequency are resonantly enhanced. Here we demonstrate that very high sensitivity can be achieved in a very simple system consisting of a Fabry-Perot cavity with CO${}_{2}$ laser thermal tuning. We demonstrate a displacement sensitivity of $\ensuremath{\sim}$$1\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}17}\phantom{\rule{0.28em}{0ex}}\text{m}/\sqrt{\text{Hz}}$, which is sufficient to observe a thermally excited acoustic mode in a 5.6 kg sapphire mirror with a signal-to-noise ratio of more than 20 dB. It is shown that a measurement sensitivity of $\ensuremath{\sim}$$2\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}20}\phantom{\rule{0.28em}{0ex}}\mathrm{m}/\sqrt{\mathrm{Hz}}$ limited by the quantum shot noise is achievable with optimization of the cavity parameters.

High-Q optomechanical GaAs nanomembranes

We present a simple fabrication method for the realization of suspended GaAs nanomembranes for cavity quantum optomechanics experiments. GaAs nanomembranes with an area of 1.36 mm by 1.91 mm and a thickness of 160 nm are obtained by using a two-step selective wet-etching technique. The frequency noise spectrum reveals several mechanical modes in the kilohertz regime with mechanical Q-factors up to 2,300,000 at room temperature. The measured mechanical mode profiles agree well with a taut rectangular drumhead model. Our results show that GaAs nanomembranes provide a promising path towards quantum optical control of massive nanomechanical systems.

Quantum superposition of massive objects and collapse models

We analyze the requirements to test some of the most paradigmatic collapse models with a protocol that prepares quantum superpositions of massive objects. This consists of coherently expanding the wave function of a ground-state-cooled mechanical resonator, performing a squared position measurement that acts as a double slit, and observing interference after further evolution. The analysis is performed in a general framework and takes into account only unavoidable sources of decoherence: blackbody radiation and scattering of environmental particles. We also discuss the limitations imposed by the experimental implementation of this protocol using cavity quantum optomechanics with levitating dielectric nanospheres.

Quantum optomechanics in the bistable regime

We study the simplest optomechanical system with a focus on the bistable regime. The covariance matrix formalism allows us to study both cooling and entanglement in a unified framework. We identify two key factors governing entanglement, namely the bistability parameter, i.e. the distance from the end of a stable branch in the bistable regime, and the effective detuning, and we describe the optimum regime where entanglement is greatest. We also show that in general entanglement is a non-monotonic function of optomechanical coupling. This is especially important in understanding the optomechanical entanglement of the second stable branch.

Optomechanical systems and quantum computing

A review of optomechanical systems is presented, including their basic components and performance data. Their role in experimental physics is discussed. Hybrid systems, whether proposed or implemented, are described in the context of building a full-scale quantum computer.

Large Quantum Superpositions and Interference of Massive Nanometer-Sized Objects

We propose a method to prepare and verify spatial quantum superpositions of a nanometer-sized object separated by distances of the order of its size. This method provides unprecedented bounds for objective collapse models of the wave function by merging techniques and insights from cavity quantum optomechanics and matter-wave interferometry. An analysis and simulation of the experiment is performed taking into account standard sources of decoherence. We provide an operational parameter regime using present-day and planned technology.

Distributing fully optomechanical quantum correlations

We present a scheme to prepare quantum correlated states of two mechanical systems based on the pouring of pre-available all-optical entanglement into the state of two micro-mirrors belonging to remote and non-interacting optomechanical cavities. We show that, under realistic experimental conditions, the protocol allows for the preparation of a genuine quantum state of a composite mesoscopic system whose non-classical features extend far beyond the occurrence of entanglement. We finally discuss a way to access such mechanical correlations.

Quantum optomechanics—throwing a glance [Invited

Mechanical resonators are gradually becoming available as new quantum systems. Quantum optics in combination with optomechanical interactions (quantum optomechanics) provides a particularly helpful toolbox for generating and controlling mechanical quantum states. We highlight some of the current challenges in the field by discussing two of our recent experiments.

Cavity Opto-Mechanics

The coupling of mechanical and optical degrees of freedom via radiation pressure has been a subject of early research in the context of gravitational wave detection. Recent experimental advances have allowed studying for the first time the modifications of mechanical dynamics provided by radiation pressure. This paper reviews the consequences of back-action of light confined in whispering-gallery dielectric microcavities, and presents a unified treatment of its two manifestations: notably the parametric instability (mechanical amplification and oscillation) and radiation pressure back-action cooling. Parametric instability offers a novel "photonic clock" which is driven purely by the pressure of light. In contrast, radiation pressure cooling can surpass existing cryogenic technologies and offers cooling to phonon occupancies below unity and provides a route towards cavity Quantum Optomechanics.

Temporal Behavior of Radiation-Pressure-Induced Vibrations of an Optical Microcavity Phonon Mode

We analyze experimentally and theoretically mechanical oscillation within an optical cavity stimulated by the pressure of circulating optical radiation. The resulting radio frequency cavity vibrations (phonon mode) cause modulation of the incident, continuous-wave (cw) input pump beam. Furthermore, with increasing cw pump power, an evolution from sinusoidal modulation to random oscillations is observed in the pump power coupled from the resonator. The temporal evolution with pump power is studied, and agreement was found with theory. In addition to applications in quantum optomechanics, the present work suggests that radiation-pressure-induced effects can establish a practical limit for the miniaturization of optical silica microcavities.