[Show abstract][Hide abstract] ABSTRACT: We investigate a hybrid quantum system consisting of a cavity optomechanical
device optically coupled to an ultracold quantum gas. We show that the
dispersive properties of the ultracold gas can be used to dramatically modify
the optomechanical response of the mechanical resonator. We examine hybrid
schemes wherein the mechanical resonator is coupled either to the motional or
the spin degrees of freedom of the ultracold gas. In either case, we find an
enhancement of more than two orders of magnitude in optomechanical cooling due
to this hybrid interaction. Significantly, based on demonstrated parameters for
the cavity optomechanical device, we identify regimes that enable the ground
state cooling of the resonator from room temperature. In addition, the hybrid
system considered here represents a powerful interface for the use of an
ultracold quantum gas for state preparation, sensing and quantum manipulation
of a mesoscopic mechanical resonator.
[Show abstract][Hide abstract] ABSTRACT: We provide a theoretical treatment of the quantum backaction of Larmor
frequency measurements on a spinor Bose-Einstein condensate by an off-resonant
light field. Two main results are presented; the first is a "quantum jump"
operator description that reflects the abrupt change in the spin state of the
atoms when a single photon is counted at a photodiode. The second is the
derivation of a conditional stochastic master equation relating the evolution
of the condensate density matrix to the measurement record. We comment on
applications of this formalism to metrology and many-body studies.
[Show abstract][Hide abstract] ABSTRACT: In this paper we present theory and simulations of an optical spring
mirror with emphasis on the incident laser beam configuration and the
associated optical trapping forces. We elucidate the physical mechanisms
underlying the optical trapping using the example of an incident
Gaussian beam and demonstrate that guided-wave trapping shows particular
promise for stable trapping in both the translational and rotational
degrees of freedom.
[Show abstract][Hide abstract] ABSTRACT: We consider theoretically the optomechanical interaction of several
mechanical modes with a single quantized cavity field mode for linear and
quadratic coupling. We focus specifically on situations where the optical
dissipation is the dominant source of damping, in which case the optical field
can be adiabatically eliminated, resulting in effective multimode interactions
between the mechanical modes. In the case of linear coupling, the coherent
contribution to the interaction can be exploited e.g. in quantum state swapping
protocols, while the incoherent part leads to significant modifications of cold
damping or amplification from the single-mode situation. Quadratic coupling can
result in a wealth of possible effective interactions including the analogs of
second-harmonic generation and four-wave mixing in nonlinear optics, with
specific forms depending sensitively on the sign of the coupling. The
cavity-mediated mechanical interaction of two modes is investigated in two
limiting cases, the resolved sideband and the Doppler regime. As an
illustrative application of the formal analysis we discuss in some detail a
two-mode system where a Bose-Einstein condensate is optomechanically linearly
coupled to the moving end mirror of a Fabry-P\'erot cavity.
Physical Review A 08/2012; 86(6). · 3.04 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: In this paper we describe a scheme for state transfer between a trapped
atomic Bose condensate and an optomechanical end-mirror mediated by a cavity
field. Coupling between the mirror and the cold gas arises from the fact that
the cavity field can produce density oscillations in the gas which in turn acts
as an internal Bragg mirror for the field. After adiabatic elimination of the
cavity field we find that the hybrid system of the gas and mirror is described
by a beam splitter Hamiltonian that allows for state transfer, but only if the
quantum nature of the cavity field is retained.
Physical Review A 02/2012; 86(2). · 3.04 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: A scheme to squeeze the center-of-mass motional quadratures of a quantum
mechanical oscillator below its standard quantum limit is proposed and analyzed
theoretically. It relies on the dipole-dipole coupling between a magnetic
dipole mounted on the tip of a cantilever to equally oriented dipoles located
on a mesoscopic tuning fork. We also investigate the influence of several
sources of noise on the achievable squeezing, including classical noise in the
driving fork and the clamping noise in the oscillator. A detection of the state
of the cantilever based on state transfer to a light field is considered. We
investigate possible limitations of that scheme.
Physical Review A 10/2011; 85(3). · 3.04 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: We study theoretically the dynamics of a hybrid optomechanical system consisting of a macroscopic mechanical membrane magnetically coupled to a spinor Bose-Einstein condensate via a nanomagnet attached at the membrane center. We demonstrate that this coupling permits us to monitor indirectly the center-of-mass position of the membrane via measurements of the spin of the condensed atoms. These measurements normally induce a significant backaction on the membrane motion, which we quantify for the cases of thermal and coherent initial states of the membrane. We discuss the possibility of measuring this quantum backaction via repeated measurements. We also investigate the potential to generate nonclassical states of the membrane, in particular Schrödinger-cat states, via such repeated measurements.
Physical Review A 08/2011; 84(2). · 3.04 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The dominant hurdle to the operation of optomechanical systems in the quantum regime is the coupling of the vibrating element to a thermal reservoir via mechanical supports. Here we propose a scheme that uses an optical spring to replace the mechanical support. We show that the resolved-sideband regime of cooling can be reached in a configuration using a high-reflectivity disk mirror held by an optical tweezer as one of the end mirrors of a Fabry-Perot cavity. We find a final phonon occupation number of the trapped mirror n=0.56 for reasonable parameters, the limit being set by our approximations, and not any fundamental physics. This demonstrates the promise of dielectric disks attached to optical springs for the observation of quantum effects in macroscopic objects.
[Show abstract][Hide abstract] ABSTRACT: We investigate the coupling of a nanomechanical oscillator in the quantum regime with molecular (electric) dipoles. We find theoretically that the cantilever can produce single-mode squeezing of the center-of-mass motion of an isolated trapped molecule and two-mode squeezing of the phonons of an array of molecules. This work opens up the possibility of manipulating dipolar crystals, which have been recently proposed as quantum memory, and more generally, is indicative of the promise of nanoscale cantilevers for the quantum detection and control of atomic and molecular systems.
[Show abstract][Hide abstract] ABSTRACT: Laser-cooled nanomechanical oscillators are promising new tools to manipulate and control ultracold atomic and molecular samples. As an illustration, we show how they can be exploited to entangle and squeeze a lattice of dipolar molecules.
[Show abstract][Hide abstract] ABSTRACT: We briefly review some of our recent and ongoing work on nanoscale optomechanics, an emerging area at the confluence of atomic,
condensed matter and gravitational wave physics. A central tenet of optomechanics is the laser cooling of a moving mirror,
typically an end mirror of a Fabry-Perot resonator, to a point near its quantum-mechanical ground state of vibration. Following
a general introduction we discuss how the motion of such a macroscopic quantum oscillator can be squeezed, and then show how
the placement of a ferroelectric tip on the oscillator allows the coherent manipulation and control of the center-of-mass
motion of ultracold polar molecules.