Publications Raphael DUMHART

2000

Articles

• S. Gardiner, D. Jaksch, R. Dumhart, J. I. Cirac, P. Zoller, Nonlinear matter wave dynamics with a chaotic potential, Phys. Rev. A 62, 023612, (2000-07-20), URL doi:10.1103/PhysRevA.62.023612 (ID: 337604) Toggle Abstract
  We consider the case of a cubic nonlinear Schrödinger equation with an additional chaotic potential, in the sense that such a potential produces chaotic dynamics in classical mechanics. We derive and describe an appropriate semiclassical limit to such a nonlinear Schrödinger equation, using a semiclassical interpretation of the Wigner function, and relate this to the hydrodynamic limit of the Gross-Pitaevskii equation used in the context of Bose-Einstein condensation. We investigate a specific example of a Gross-Pitaevskii equation with such a chaotic potential, the one-dimensional delta-kicked harmonic oscillator, and its semiclassical limit, discovering in the process an interesting interference effect, where increasing the strength of the repulsive nonlinearity promotes localization of the wave function. We explore the feasibility of an experimental realization of such a system in a Bose-Einstein condensate experiment, giving a concrete proposal of how to implement such a configuration, and considering the problem of condensate depletion.

1998

Articles

• R. Dumhart, J. I. Cirac, M. Lewenstein, P. Zoller, Creation of Dark Solitons and Vortices in Bose-Einstein Condensates, Phys. Rev. Lett. 80, 2972, (1998-04-06), URL doi:10.1103/PhysRevLett.80.2972 (ID: 367776) Toggle Abstract
  We propose and analyze a scheme to create dark solitons and vortices in Bose-Einstein condensates. This is achieved starting from a condensate in the internal state |a> and transferring the atoms to the internal state |b> via a Raman transition induced by laser light. By scanning adiabatically the Raman detuning, dark solitons and vortices are created.

1994

Articles

• R. Dumhart, P. Marte, T. Pellizzari, P. Zoller, Laser Cooling to a Single Quantum State in a Trap, Physical Review Letters 73, 2829–2832, (1994-11-21), URL doi:10.1103/PhysRevLett.73.2829 (ID: 375181) Toggle Abstract
  Laser cooling in a trap is investigated for configurations which allow the existence of "dark states" of the combined atom-plus-trap system, i.e., states which are decoupled from the laser light by quantum interference. Two examples of approximate dark states in a 1D flat bottom and 2D harmonic trap for angular momentum 1 to 1 transitions are discussed. A wave function simulation of the quantum master equation predicts that a significant fraction of the atoms are transferred to a single trap state. ©1994 The American Physical Society
• P. Marte, R. Dumhart, R. Taïeb, P. Zoller, M. S. Shahriar, M. Prentiss, Polarization-gradient-assisted subrecoil cooling: Quantum calculations in one dimension, Physical Review A 49, 4826–4836, (1994-06-06), URL doi:10.1103/PhysRevA.49.4826 (ID: 375174) Toggle Abstract
  We present a fully quantum-mechanical analysis of laser cooling of an angular momentum Jg=1 to Je=1 transition in a laser configuration consisting of two counterpropagating linearly polarized laser beams. The essential feature of this configuration is the coexistence of velocity-selective coherent population trapping (VSCPT) and polarization-gradient cooling. The role of polarization-gradient cooling is to provide (i) for short interaction times ‘‘precooling’’ of the initial momentum distribution and (ii) in the long-time limit ‘‘confinement of velocities.’’ This eventually leads to a larger number of atoms being captured in the dark state when compared with the schme of Aspect et al. [Phys. Rev. Lett. 61, 826 (1988)]. We find that the optimum parameter values for polarization-gradient cooling and VSCPT are in a completely different parameter regime: polarization-gradient cooling works best off resonance and for low intensities, while VSCPT works best on resonance. We can combine the advantages of polarization-gradient cooling and VSCPT in a scheme where we cycle in time between the optimum cooling parameters for both cooling mechanisms. ©1994 The American Physical Society
• R. Taïeb, R. Dumhart, J. I. Cirac, P. Marte, P. Zoller, Cooling and localization of atoms in laser-induced potential wells, Physical Review A 49, 4876–4887, (1994-06-06), URL doi:10.1103/PhysRevA.49.4876 (ID: 375172) Toggle Abstract
  We discuss theoretically the cooling and localization of atoms in deep potentials induced by a far-off-resonant standing-wave laser. For a two-level atom cooling occurs via a Sisyphus mechanism. For a Λ system we discuss a Raman cooling scheme similar to the one proposed for laser cooling in ion traps. ©1994 The American Physical Society

1993

Articles

• P. Marte, R. Dumhart, R. Taïeb, P. D. Lett, P. Zoller, Quantum wave function simulation of the resonance fluorescence spectrum from one-dimensional optical molasses, Phys. Rev. Lett. 71, 1335–1338, (1993-08-09), URL doi:10.1103/PhysRevLett.71.1335 (ID: 375416) Toggle Abstract
  Using recently developed quantum wave function techniques, we have performed a simulation of 85Rb atoms in a one-dimensional optical molasses, formed from counterpropagating laser beams with orthogonal linear polarizations. Both internal and external degrees of freedom are treated quantum mechanically in one dimension and the spectrum of resonance fluorescence is calculated and compared to recent experiments. Excellent agreement is obtained for the spectrum and additional insight is gained into the experimental evidence for quantized motion in the optical potentials. ©1993 The American Physical Society
• P. Marte, R. Dumhart, R. Taïeb, P. Zoller, Resonance fluorescence from quantized one-dimensional molasses, Phys. Rev. A 47, 1378–1390, (1993-02-02), URL doi:10.1103/PhysRevA.47.1378 (ID: 375414) Toggle Abstract
  We study theoretically the spectrum of resonance fluoresence from one-dimensional molasses consisting of two-level atoms with Zeeman substructure. The center-of-mass motion of the atom is treated fully quantum mechanically. The spectrum shows sidebands due to transitions between vibrational levels in optical potentials generated by the laser light. Detailed results are presented for the Jg=1/2→Je=3/2 atomic transition in a laser configuration with two counterpropagating waves with orthogonal polarizations. We have solved the corresponding quantum master equation and calculated the relevant autocorrelation function of the atomic dipole using (i) a direct numerical solution of the master equation, (ii) a wave-function simulation of the master equation and correlation function employing periodic time-dependent Bloch wave functions, and (iii) a semiclassical bipotential calculation for the spectrum including a simple quantum correction. ©1993 The American Physical Society
• R. Taïeb, P. Marte, R. Dumhart, P. Zoller, Spectrum of resonance fluorescence and cooling dynamics in quantized one-dimensional molasses: Effects of laser configuration, Phys. Rev. A 47, 4986–4993, (1993-06-06), URL doi:10.1103/PhysRevA.47.4986 (ID: 375409) Toggle Abstract
  We study theoretically the spectrum of resonance fluorescence and laser-cooling dynamics corresponding to quantized atomic motion in one-dimensional optical molasses. We consider an atom with a Jg=1→Je=2 transition interacting with two counterpropagating laser beams. The laser light is assumed to be linearly polarized with an angle θ between the polarization vectors. We discuss the spectrum of resonance fluorescence, the spectroscopy of band structure in the optical potentials, and the population of the vibrational quantum levels as a function of the angle between the polarization vectors. ©1993 The American Physical Society

1992

Articles

• R. Dumhart, P. Zoller, H. Ritsch, Monte Carlo simulation of the atomic master equation for spontaneous emission, Phys. Rev. A 45, 4879–4887, (1992-04-01), URL doi:10.1103/PhysRevA.45.4879 (ID: 375891) Toggle Abstract
  A Monte Carlo simulation of the atomic master equation for spontaneous emission in terms of atomic wave functions is developed. Realizations of the time evolution of atomic wave functions are constructed that correspond to an ensemble of atoms driven by laser light undergoing a sequence of spontaneous emissions. The atomic decay times are drawn according to the photon count distribution of the driven atom. Each quantum jump of the atomic electron projects the atomic wave function to the ground state of the atom. Our theory is based on a stochastic interpretation and generalization of Mollow’s pure-state analysis of resonant light scattering, and the Srinivas-Davies theory of continuous measurements in photodetection. An extension of the theory to include mechanical light effects and a generalization to atomic systems with Zeeman substructure are given. We illustrate the method by simulating the solutions of the optical Bloch equations for two-level systems, and laser cooling of a two-level atom in an ion trap where the center-of-mass motion of the atom is described quantum mechanically. ©1992 The American Physical Society
• R. Dumhart, A. S. Parkins, P. Zoller, Gardiner, Crispin, Monte Carlo simulation of master equations in quantum optics for vacuum, thermal, and squeezed reservoirs, Phys. Rev. A 46, 4382–4396, (1992-10-01), URL doi:10.1103/PhysRevA.46.4382 (ID: 375893) Toggle Abstract
  Wave-function simulation of the master equation in terms of quantum jumps is illustrated for vacuum, thermal, and squeezed reservoirs. We discuss simulation techniques for (i) atomic density matrices, and resonance fluoresence and weak-field absorption spectra of atoms, (ii) decay of a two-level system in a squeezed vacuum, and (iii) a strongly coupled atom-cavity system driven by thermal light. ©1992 The American Physical Society