arXiv subjects

P. Meystre

Publications and source records attributed to P. Meystre.

At least 37 records · Page 2Linked to original sources

arXiv2011

Quantum optomechanics of a Bose-Einstein Antiferromagnet

We investigate the cavity optomechanical properties of an antiferromagnetic Bose-Einstein con- densate, where the role of the mechanical element is played by spin-wave excitations. We show how this system can be described by a single rotor that can be prepared deep in the quantum regime under realizable experimental conditions. This system provides a bottom-up realization of dispersive rotational optomechanics, and opens the door to the direct observation of quantum spin fluctuations.

quant-ph↗

arXiv2011

Slow-light probe of Fermi pairing through an atom-molecule dark state

We consider the two-color photooassociation of a quantum degenerate atomic gas into ground-state diatomic molecules via a molecular dark state. This process can be described in terms of a lambda level scheme that is formally analogous to the situation in electromagnetically-induced transparency (EIT) in atomic systems, and therefore can result in slow light propagation. We show that the group velocity of the light field depends explicitly on whether the atoms are bosons or fermions, as well as on the existence or absence of a pairing gap in the case of fermions, so that the measurement of the group velocity realizes a non-destructive diagnosis of the atomic state and the pairing gap.

cond-mat.quant-gas↗

arXiv2011

Spinor atom-molecule conversion via laser-induced three-body recombination

We study theoretically several aspects of the dynamics of coherent atom-molecule conversion in spin-1 Bose-Einstein condensates. Specifically, we discuss how for a suitable dark-state condition the interplay of spin-exchange collisions and photoassociation leads to the stable creation of an atom- molecule pairs from three initial spin-zero atoms. This process involves two two-body interactions and can be intuitively viewed as an effective three-body recombination. We investigate the relative roles of photoassociation and of the initial magnetization in the \resonant" case where the dark state condition is perfectly satisfied. We also consider the "non-resonant" regime, where that condition is satisfied either approximately {the so-called adiabatic case {or not at all. In the adiabatic case, we derive an effective non-rigid pendulum model that allows one to conveniently discuss the onset of an antiferromagnetic instability of an \atom-molecule pendulum," as well as large-amplitude pair oscillations and atom-molecule entanglement.

cond-mat.quant-gas↗

arXiv2010

Towards all-optical optomechanics: An optical spring mirror

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 ${\bar n}$= 0.14 for reasonable parameters, well within the quantum regime. This demonstrates the promise of dielectric disks attached to optical springs for the observation of quantum effects in macroscopic objects.

quant-ph↗

arXiv2010

Laser-catalyzed spin-exchange process in a Bose-Einstein condensate

We show theoretically that it is possible to optically control collective spin-exchange processes in spinor Bose condensates through virtual photoassociation. The interplay between optically induced spin exchange and spin-dependent collisions provides a flexible tool for the control of atomic spin dynamics, including enhanced or inhibited quantum spin oscillations, the optically-induced ferromagnetic-to-antiferromagnetic transition, and coherent matter-wave spin conversion.

quant-ph↗

arXiv2010

Classical dynamics of the optomechanical modes of a Bose-Einstein condensate in a ring cavity

We consider a cavity optomechanical system consisting of a Bose-Einstein condensate (BEC) interacting with two counterpropagating traveling-wave modes in an optical ring cavity. In contrast to the more familiar case where the condensate is driven by the standing-wave field of a high-$Q$ Fabry-P{é}rot cavity we find that both symmetric and antisymmetric collective density side modes of the BEC are mechanically excited by the light field. In the semiclassical, mean-field limit where the light field and the zero-momentum mode of the condensate are treated classically the system is found to exhibit a rich multistable behavior, including the appearance of isolated branches of solutions (isolas). We also present examples of the dynamics of the system as input parameters such as the frequency of the driving lasers are varied.

cond-mat.quant-gas↗

arXiv2010

Optomechanics of a Quantum-Degenerate Fermi Gas

We explore theoretically the optomechanical interaction between a light field and a mechanical mode of ultracold fermionic atoms inside a Fabry-Pérot cavity. The low-lying phonon mode of the fermionic ensemble is a collective density oscillation associated with particle-hole excitations, and is mathematically analogous to the momentum side-mode excitations of a bosonic condensate. The mechanical motion of the fermionic particle-hole system behaves hence as a ``moving mirror.'' We derive an effective system Hamiltonian that has the form of generic optomechanical systems. We also discuss the experimental consequences the optomechanical coupling in optical bistability and in the noise spectrum of the system.

quant-ph↗

arXiv2009

Dynamics of a bistable Mott insulator to superfluid phase transition in cavity optomechanics

We study the dynamics of the many-body state of ultracold bosons trapped in a bistable optical lattice in an optomechanical resonator controlled by a time-dependent input field. We focus on the dynamics of the many-body system following discontinuous jumps of the intracavity field. We identify experimentally realizable parameters for the bistable quantum phase transition between Mott insulator and superfluid.

quant-ph↗

arXiv2009

Hamiltonian chaos in a coupled BEC -- optomechanical cavity system

We study a hybrid optomechanical system consisting of a Bose-Einstein condensate (BEC) trapped inside a single-mode optical cavity with a moving end-mirror. The intracavity light field has a dual role: it excites a momentum side-mode of the condensate, and acts as a nonlinear spring that couples the vibrating mirror to that collective density excitation. We present the dynamics in a regime where the intracavity optical field, the mirror, and the side-mode excitation all display bistable behavior. In this regime we find that the dynamics of the system exhibits Hamiltonian chaos for appropriate initial conditions.

quant-ph↗

arXiv2009

Quantum Mechanical Limits to Inertial Mass Sensing by Nanomechanical Systems

We determine the quantum mechanical limits to inertial mass-sensing based on nanomechanical systems. We first consider a harmonically oscillating cantilever whose vibration frequency is changed by mass accretion at its surface. We show that its zero-point fluctuations limit the mass sensitivity, for attainable parameters, to about an electron mass. In contrast to the case of a classical cantilever, we find the mass sensitivity of the quantum mechanical cantilever is independent of its resonant frequency in a certain parameter regime at low temperatures. We then consider an optomechanical setup in which the cantilever is reflective and forms one end of a laser-driven Fabry-Pérot cavity. For a resonator finesse of 5 the mass sensitivity at T=0 is limited by cavity noise to about a quarter of a Dalton, but this setup has a more favorable temperature dependency at finite temperature, compared to the free cantilever.

quant-ph↗

arXiv2009

Bistable Mott-insulator to superfluid phase transition in cavity optomechanics

We study the many-body state of ultracold bosons in a bistable optical lattice potential in an optomechanical resonator in the weak-coupling limit. New physics arises as a result of bistability and discontinuous jumps in the cavity field. Of particular interest is the situation where the optical cavity is engineered so that a single input beam can result in two radically different stable ground states for the intracavity gas: superfluid and Mott-insulator.

quant-ph↗

arXiv2009

Coherent bimolecular reactions with quantum-degenerate matter waves

We demonstrate theoretically that the abstraction reaction $A+B_2 \to AB+B$ can be driven coherently and efficiently with quantum-degenerate bosonic or fermionic matter waves. We show that the initial stages of the reaction are dominated by quantum fluctuations, resulting in the appearance of macroscopic non-classical correlations in the final atomic and molecular fields. The dynamics associated with the creation of bosonic and of fermionic dimer-atom pairs are also compared. This study opens up a promising new regime of quantum degenerate matter-wave chemistry.

quant-ph↗

arXiv2008

Cavity QED characterization of many-body atomic states in double-well potentials -- The role of dissipation

When an incident light beam is scattered off a sample of ultracold atoms trapped in an optical lattice, the statistical properties of the retro-reflected field contain information about the quantum state of the atoms, and permit for example to distinguish between atoms in a superfluid and a Mott insulator state. This paper extends our previous analysis of this problem to include the effects of cavity damping. We use a Monte Carlo wave function method to determine the two-time correlation function and time-dependent physical spectrum of the retro-reflected field in the case of a simple two-well lattice. We also analyze quantitatively the entanglement between the atoms and the light field for atoms in a Mott insulator and a superfluid state.

quant-ph↗

arXiv2008

Quantum Noise in the Collective Abstraction Reaction A+B $_2\to$ AB+B

We demonstrate theoretically that the collective abstraction reaction A+B$_2 \to$ AB+B can be realized efficiently with degenerate bosonic or fermionic matter waves. We show that this is dominated by quantum fluctuations, which are critical in triggering its initial stages with the appearance of macroscopic non-classical correlations of the atomic and molecular fields as a result. This study opens up a promising new regime of quantum degenerate matter-wave chemistry.

quant-ph↗

arXiv2008

Stability of the density-wave state of a dipolar condensate in a pancake trap

We study a dipolar boson-fermion mixture in a pancake geometry at absolute zero temperature, generalizing our previous work on the stability of polar condensates and the formation of a density-wave state in cylindrical traps. After examining the dependence of the polar condensate stability on the strength of the fermion-induced interaction, we determine the transition point from a ground-state Gaussian to a hexagonal density-wave state. We use a variational principle to analyze the stability properties of those density-wave state.

cond-mat.other↗

arXiv2008

Coupling nanomechanical cantilevers to dipolar molecules

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.

quant-ph↗

arXiv2008

Superradiant Raman scattering in an ultracold Bose gas at finite temperature

We study superradiant Raman scattering from an ultra-cold, but finite temperature Bose gas in a harmonic trap. Numerical simulations indicate the existence of distinct timescales associated with the decoherence of the condensed versus thermal fractions, and the concomitant preferred scattering from atoms in low lying trap states in the regime where superradiance takes place on a timescale comparable to an inverse trap frequency. As a consequence the scattered atoms experience a modest reduction in temperature as compared to the unscattered atoms.

physics.atom-ph↗

arXiv2008

Multiple membrane cavity optomechanics

We investigate theoretically the extension of cavity optomechanics to multiple membrane systems. We describe such a system in terms of the coupling of the collective normal modes of the membrane array to the light fields. We show these modes can be optically addressed individually and be cooled, trapped and characterized, e.g. via quantum nondemolition measurements. Analogies between this system and a linear chain of trapped ions or dipolar molecules imply the possibility of related applications in the quantum regime.

quant-ph↗