Papers by M. Fleischhauer
Europhysics Letters (EPL), 1998
Matsubara Green's functions for interacting bosons are expressed as classical statistical average... more Matsubara Green's functions for interacting bosons are expressed as classical statistical averages corresponding to a linear imaginary-time stochastic differential equation. This makes direct numerical simulations applicable to the study of equilibrium quantum properties of bosons in the non-perturbative regime. To verify our results we discuss an oscillator with quartic anharmonicity as a prototype model for an interacting Bose gas. An analytic expression for the characteristic function in a thermal state is derived and a Higgs-type phase transition discussed, which occurs when the oscillator frequency becomes negative.
Lithuanian Journal of Physics
We propose a new method of creating solitons in elongated Bose-Einstein Condensates (BECs) by swe... more We propose a new method of creating solitons in elongated Bose-Einstein Condensates (BECs) by sweeping three laser beams through the BEC. If one of the beams is in the first order (TEM10) Hermite-Gaussian mode, its amplitude has a transversal π phase slip which can be transferred to the atoms creating a soliton. Using this method it is possible to circumvent the restriction set by the diffraction limit inherent to conventional methods such as phase imprinting. The method allows one to create multicomponent (vector) solitons of the dark-bright form as well as the dark-dark combination. In addition it is possible to create in a controllable way two or more dark solitons with very small velocity and close to each other for studying their collisional properties.
Quantum Optics: Journal of the European Optical Society Part B
Abstract. We review the'effects of density dependent near dipole-dipole, or local field, int... more Abstract. We review the'effects of density dependent near dipole-dipole, or local field, interactions on lasing without inversion. In particular. we consider the nonlinear behaviour of the macroscopic electric susceptibility of a dense, coherently prepared, three-level A system. For certain values of the atomic density, we observe enhancement of the absorptionless index of refraction and inversionless gain by more than two orders of magnitude. We also predict a piezophotonic switching effect whereby a small change in density induces the ...
Technical Digest. Summaries of papers presented at the Quantum Electronics and Laser Science Conference. Postconference Technical Digest (IEEE Cat. No.01CH37172), 2000
ABSTRACT Summary form only given. We describe a technique that allows one to transfer quantum cor... more ABSTRACT Summary form only given. We describe a technique that allows one to transfer quantum correlations from traveling-wave light fields to collective atomic states and vice versa with nearly ideal efficiency. This is achieved by adiabatically reducing the group velocity of light to zero, thereby "trapping" the photons in the medium.
Plasmonics: Metallic Nanostructures and Their Optical Properties X, 2012
Technical Digest. Summaries of Papers Presented at the Quantum Electronics and Laser Science Conference, 1999
ABSTRACT Summary form only given. Theoretical and experimental work of past few years on atomic c... more ABSTRACT Summary form only given. Theoretical and experimental work of past few years on atomic coherence and interference has demonstrated a potential to improve significantly the existing nonlinear optical techniques. In this contribution we present theoretical and experimental results demonstrating the possibility of efficient parametric oscillation in Raman-like double-Δ systems. We discuss the possible applications of this process for quantum noise suppression and nonlinear mixing at a very low (few photon) power level
Essays in Honor of Edwin T. Jaynes, 1993
Physical Review A, 2003
We investigate the spontaneous radiation from a two-level atom embedded in a three-dimensional an... more We investigate the spontaneous radiation from a two-level atom embedded in a three-dimensional anisotropic photonic crystal with two bands. The properties of the spontaneous emission are dependent strongly on the position of the upper level. The faster and slower decay components can occur in the emitted field, but it does not mean the existence of both accelerated and inhibited components for the atomic population decay. The radiation spectrum is dependent on the location of the observer. We also study the influence of the existence of the two bands on spontaneous emission, Lamb shift, the emitted field, and the radiation spectrum.
Physical Review A, 2003
We analyze both analytically and numerically the resonant four-wave mixing of two co-propagating ... more We analyze both analytically and numerically the resonant four-wave mixing of two co-propagating single-photon wave packets. We present analytic expressions for the two-photon wave function and show that soliton-type quantum solutions exist which display a shape-preserving oscillatory exchange of excitations between the modes. Potential applications including quantum information processing are discussed.
Physical Review B, 2015
We discuss a protocol for growing states with topological order in interacting many-body systems ... more We discuss a protocol for growing states with topological order in interacting many-body systems using a sequence of flux quanta and particle insertion. We first consider a simple toy model, the superlattice Bose Hubbard model, to explain all required ingredients. Our protocol is then applied to fractional quantum Hall systems in both, continuum and lattice. We investigate in particular how the fidelity, with which a topologically ordered state can be grown, scales with increasing particle number N . For small systems exact diagonalization methods are used. To treat large systems with many particles, we introduce an effective model based on the composite fermion description of the fractional quantum Hall effect. This model also allows to take into account the effects of dispersive bands and edges in the system, which will be discussed in detail.
Optics and Photonics News, 2006
Physical review. E, Statistical, nonlinear, and soft matter physics, 2003
We investigate the dynamical properties of the radiation field emitted from an excited two-level ... more We investigate the dynamical properties of the radiation field emitted from an excited two-level atom in a photonic crystal. If the transition frequency of the atom lies within a certain frequency range above the band edge, the emitted field consists of two components that show a different decay dynamics. In particular it is shown that one field component decreases faster than the atomic population with a decay constant depending on the distance from the atom. As a consequence, the decay rate of the electromagnetic field is spatially varying and, in general, can not be identified with the corresponding rate for the atomic population.
Quantum Information with Continuous Variables of Atoms and Light, 2007
Coherence and Quantum Optics VIII, 2003
A coherent technique for the control of photon propagation in optically thick media and its appli... more A coherent technique for the control of photon propagation in optically thick media and its application for quantum memories is discussed. Raman adiabatic passage with an externally controlled Stokes field can be used to transfer the quantum state of a light pulse ("flying" qubit) to a collective spin-excitation (stationary qubit) and thereby slow down its propagation velocity to zero. The process is reversible and has a potential fidelity of unity without the necessity for strongly coupling resonators. A simple quasi-particle picture (dark-state polariton) of the transfer is presented. The analytic theory is supplemented with exact numerical solutions. Finally the influence of decoherence mechanisms on collective storage states, which are N -particle entangled states, is analyzed.
Physical Review A, 2004
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Abstract—We study the effect of near dipole–dipole interactions on the electric susceptibility of... more Abstract—We study the effect of near dipole–dipole interactions on the electric susceptibility of a coherently prepared collection of three-level atoms in the Λ-configuration. In particular, we discuss two optical switching mechanisms and mention possible interesting applications. Finally, we use an optimal control technique to optimize the desired atomic response in, eg, piezophotonic and magnetophotonic switching.
Two atoms put at the foci of a perfect lens [J.B. Pendry, Phys. Ref. Lett. 85, 3966 (2000)] are s... more Two atoms put at the foci of a perfect lens [J.B. Pendry, Phys. Ref. Lett. 85, 3966 (2000)] are shown to exhibit perfect sub-and super-radiance even over macroscopic distances limited only by the propagation length in the free-space decay time. If the left-handed material forming the perfect lens has nearly constant negative refraction and vanishing absorption over a spectral range larger than the natural linewidth, the imaginary part of the retarded Greens-function between the two focal points is identical to the one at the same spatial position and the atoms undergo a Markovian dynamics. Collective decay rates and level shifts are calculated from the Greens-function of the Veselago-Pendry lens and limitation as well as potential applications are discussed. PACS numbers: 42.50.Fx,78.20.Ci,41.20.Jb Negative refraction of electromagnetic radiation in materials with simultaneous negative dielectric positivity ε and magnetic permeability µ was first predicted by Veselago [1]. These so-called left-handed media attracted much attention recently because of possible realizations in metamaterials [2, 3, 4, 5, 6] and their application for a lens without diffraction limitations . An infinite parallel slab of lossless left-handed material of thickness d collects all plane waves from a point source on one side of the slab not too far away from the surface in a focal point on the other side. If the medium has a refractive index of n = −1 the distance between the two foci is 2d. As pointed out by Pendry [7], the lens formed by the slab is perfect in the sense that the amplitudes of evanescent waves emerging from the source are amplified in the left handed medium (LHM) and exactly reproduced at the focal point thus leading to an image not limited by diffraction. This raises the question what happens to two atoms with radiative transitions inside the frequency range of negative refraction put in the focal points of a Veselago-Pendry lens.
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Papers by M. Fleischhauer