Theoretical scheme for the realization of the sphere-coherent motional states in an atom-assisted optomechanical cavity (original) (raw)
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Cavity quantum optomechanics of ultracold atoms in an optical lattice: Normal-mode splitting
2009
We consider the dynamics of a movable mirror (cantilever) of a cavity coupled through radiation pressure to the light scattered from ultracold atoms in an optical lattice. Scattering from different atomic quantum states creates different quantum states of the scattered light, which can be distinguished by measurements of the displacement spectrum of the cantilever. We show that for large pump intensities the steady state displacement of the cantilever shows bistable behaviour. Due to atomic back-action, the displacement spectrum of the cantilever is modified and depends on the position of the condensate in the Brillouin zone. We further analyze the occurrence of splitting of the normal mode into three modes due to mixing of the mechanical motion with the fluctuations of the cavity field and the fluctuations of the condensate with finite atomic two-body interaction. The present system offers a novel scheme to coherently control ultracold atoms as well as cantilever dynamics.
Quantum Effects in Optomechanical Systems
Advances in Atomic, Molecular, and Optical Physics, Vol 57, 2009
The search for experimental demonstrations of the quantum behavior of macroscopic mechanical resonators is a fastly growing field of investigation and recent results suggest that the generation of quantum states of resonators with a mass at the microgram scale is within reach. In this chapter we give an overview of two important topics within this research field: cooling to the motional ground state, and the generation of entanglement involving mechanical, optical and atomic degrees of freedom. We focus on optomechanical systems where the resonator is coupled to one or more driven cavity modes by the radiation pressure interaction. We show that robust stationary entanglement between the mechanical resonator and the output fields of the cavity can be generated, and that this entanglement can be transferred to atomic ensembles placed within the cavity. These results show that optomechanical devices are interesting candidates for the realization of quantum memories and interfaces for continuous variable quantum communication networks.
Cold-Atom-Induced Control of an Optomechanical Device
Physical Review Letters, 2010
We consider an optical cavity with a light vibrating end-mirror and containing a Bose-Einstein condensate (BEC). The mediation of the cavity field induces a non-trivial interplay between the mirror and the collective oscillations of the intra-cavity atomic density. We explore the thermodynamical implications of this dynamics and highlight the possibilities for indirect diagnostic. The effects we discuss can be observed in a set-up that is well within reach of current experimental capabilities and is central in the quest for mesoscopic quantumness.
Optomechanical control of atoms and molecules
Laser Physics, 2010
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 opto mechanics 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 place ment of a ferroelectric tip on the oscillator allows the coherent manipulation and control of the center of mass motion of ultracold polar molecules.
Cavity optomechanical coupling assisted by an atomic gas
2008
We theoretically study a cavity filled with atoms, which provides the optical-mechanical interaction between the modified cavity photonic field and a movable mirror at one end. We show that the cavity field "dresses" these atoms, producing two types of polaritons, effectively enhancing the radiation pressure of the cavity field upon the end mirror, as well as establishing an additional squeezing mode of the end mirror. This squeezing produces an adiabatic entanglement, which is absent in usual vacuum cavities, between the oscillating mirror and the rest of the system. We analyze the entanglement and quantify it using the Loschmidt echo and fidelity.
Journal of Physics B: Atomic, Molecular and Optical Physics, 2011
We propose a theoretical scheme to show the possibility of generating motional nonlinear coherent states and their superposition for an undamped vibrating micromechanical membrane inside an optical cavity. The scheme is based on an intensity-dependent coupling of the membrane to the radiation pressure field. We show that if the cavity field is initially prepared in a Fock state, the motional state of the membrane may evolve from vacuum state to a special type of nonlinear coherent states. By examining the nonclassical properties of the generated state of the membrane, including the quadrature squeezing and the sub-Poissonian statistics, we find that by varying the Lamb-Dicke parameter and the membrane's reflectivity one can effectively control those properties. In addition, the scheme offers the possibility of generating various types of the so-called nonlinear multicomponent Schrödinger cat sates of the membrane. We also examine the effect of the damping of the cavity field on the motional state of the membrane. and entanglement at a macroscopic scale .
Resolving the vacuum fluctuations of an optomechanical system using an artificial atom
Nature Physics, 2015
Heisenberg's uncertainty principle results in one of the strangest quantum behaviors: an oscillator can never truly be at rest. Even in its lowest energy state, at a temperature of absolute zero, its position and momentum are still subject to quantum fluctuations. Resolving these fluctuations using linear position measurements is complicated by the fact that classical noise can masquerade as quantum noise. On the other hand, direct energy detection of the oscillator in its ground state makes it appear motionless. So how can we resolve quantum fluctuations? Here, we parametrically couple a micromechanical oscillator to a microwave cavity to prepare the system in its quantum ground state and then amplify the remaining vacuum fluctuations into real energy quanta. Exploiting a superconducting qubit as a photon/phonon number resolving detector we provide the essential nonlinear resource to authenticate the unambiguously quantum nature of both light and motion. Our results further demonstrate the ability to control a long-lived mechanical oscillator using a non-Gaussian resource, directly enabling applications in quantum information processing and enhanced detection of displacement and forces.
In this paper, we study theoretically bipartite and tripartite continuous variable entanglement as well as normal-mode splitting in a single-atom cavity optomechanical system with intensity-dependent coupling. The system under consideration is formed by a Fabry-Pérot cavity with a thin vibrating end mirror and a two-level atom in the Gaussian standing wave of the cavity mode. We first derive the general form of the Hamiltonian describing the tripartite intensity-dependent atom-field-mirror coupling due to the presence of the cavity mode structure. We then restrict our treatment to the first vibrational sideband of the mechanical resonator and derive a tripartite atom-field-mirror Hamiltonian. We show that when the optical cavity is intensely driven, one can generate bipartite entanglement between any pair in the tripartite system and that, due to entanglement sharing, atom-mirror entanglement is efficiently generated at the expense of optical-mechanical and optical-atom entanglement. We also find that in such a system, when the Lamb-Dicke parameter is large enough, one can simultaneously observe the normal mode splitting into three modes. PACS number(s): 37.30.+i, 03.67.Bg, 42.50.Wk, 85.85.+j