TY  - JOUR
A1  - Albus, Alexander P.
A1  - Gardiner, Simon A.
A1  - Illuminati, Fabrizio
A1  - Wilkens, Martin
T1  - Quantum field theory of dilute homogeneous Bose-Fermi-mixtures at zero temperature : general formalismand beyond mean-field corrections
N2  - We consider a dilute homogeneous mixture of bosons and spin-polarized fermions at zero temperature. We first construct the formal scheme for carrying out systematic perturbation theory in terms of single particle Green's functions. We introduce a new relevant object, the renormalized boson-fermion T-matrix which we determine to second order in the boson-fermion s-wave scattering length. We also discuss how to incorporate the usual boson-boson T-matrix in mean-field approximation to obtain the total ground state properties of the system. The next order term beyond mean- field stems from the boson-fermion interaction and is proportional to $a_{scriptsize BF}k_{scriptsize F}$. The total ground-state energy-density reads $E/V =epsilon_{scriptsize F} + epsilon_{scriptsize B} + (2pihbar^{2}a_{
m BF}n_{scriptsize B}n_{scriptsize F}/m) [1 + a_{scriptsize BF}k_{scriptsize F}f(delta)/pi]$. The first term is the kinetic energy of the free fermions, the second term is the boson-boson mean-field interaction, the pre-factor to the additional term is the usual mean-field contribution to the boson-fermion interaction energy, and the second term in the square brackets is the second-order correction, where $f(delta)$ is a known function of $delta= (m_{scriptsize B} - m_{scriptsize F})/(m_{scriptsize B} + m_{scriptsize F})$. We discuss the relevance of this new term, how it can be incorporated into existing theories of boson-fermion mixtures, and its importance in various parameter regimes, in particular considering mixtures of $^{6}$Li and $^{7}$Li and of $^{3}$He and $^{4}$He.
Y1  - 2002
UR  - http://xxx.lanl.gov/abs/cond-mat/0201102
ER  - 
TY  - JOUR
A1  - Albus, Alexander P.
A1  - Illuminati, Fabrizio
A1  - Wilkens, Martin
T1  - Ground-state properties of trapped Bose-Fermi mixtures: Role of exchange correlation
Y1  - 2003
ER  - 
TY  - JOUR
A1  - Busch, Thomas
A1  - Englert, Bertold-Georg
A1  - Rzazewski, Kazimierz
A1  - Wilkens, Martin
T1  - Two cold atoms in a harmonic trap
N2  - Two ultracold atoms moving in a trap interact weakly at a very short distance. This interaction can be modeled by a properly regularized contact potential. We solve the corresponding time-independent Schrödinger equation under the assumption of a parabolic, spherically symmetric trapping potential.
Y1  - 1998
ER  - 
TY  - JOUR
A1  - Eisert, Jens
A1  - Felbinger, Timo
A1  - Papadopolous, P.
A1  - Plenio, M. B.
A1  - Wilkens, Martin
T1  - Classical information and distillable entanglement
N2  - We establish a quantitative connection between the amount of lost classical information about a quantum state and the concomitant loss of entanglement. Using menthods that have been developed for the optimal purification of miced states, we find a class of miced states with known distillable entanglement. These results can be used to determine the quantum capacity of a quantum channel which randomizes the order of transmitted signals.
Y1  - 2000
ER  - 
TY  - JOUR
A1  - Eisert, Jens
A1  - Wilkens, Martin
T1  - Catlysis of Entanglement Manipulation for Mixed States
N2  - We consider entanglement-assisted remote quantum state manipulation of bipartite mixed states. Several aspects are addressed: we present a class of mixed states of rank two that can be transformed into another class of mixed states under entanglement-assisted local operations with classical communication, but for which such a transformation is impossible without assistance. Furthermore, we demonstrate enhancement of the efficiency of purification protocols with the help of entanglement-assisted operations. Finally, transformations from one mixed state to mixed target states which are sufficiently close to the source state are contrasted with similar transformations in the pure-state case.
Y1  - 2000
ER  - 
TY  - JOUR
A1  - Eisert, Jens
A1  - Wilkens, Martin
T1  - Quantum games
N2  - In these lecture notes we investigate the implications of the identification of strategies with quantum operations in game theory beyond the results presented in [J. Eisert, M. Wilkens, and M. Lewenstein, Phys. Rev. Lett. 83, 3077 (1999)]. After introducing a general framework, we study quantum games with a classical analogue in order to flesh out the peculiarities of game theoretical settings in the quantum domain. Special emphasis is given to a detailed investigation of different sets of quantum strategies.
Y1  - 2000
UR  - http://xxx.lanl.gov/abs/quant-ph/0004076
ER  - 
TY  - JOUR
A1  - Eisert, Jens
A1  - Wilkens, Martin
A1  - Lewenstein, Maciej
T1  - Quantum Games and Quantum Strategies
N2  - We investigate the quantization of nonzero sum games. For the particular case of the Prisoners' Dilemma we show that this game ceases to pose a dilemma if quantum strategies are allowed for. We also construct a particular quantum strategy which always gives reward if played against any classical strategy.
Y1  - 1999
ER  - 
TY  - JOUR
A1  - Felbinger, Timo
A1  - Santos, L.
A1  - Wilkens, Martin
A1  - Lewenstein, Maciej
T1  - Time Correlations of a laser-induced Bose-Einstein condensate
N2  - We analyze the multi-time correlations of a laser-induced Bose Einstein condensate. We use quantum stochastic methods to obtain under certain circumstances a Fokker-Planck equation which describes the phase-difussion process, and obtain an analytical expression of the two-time correlations. We perform also quantum Monte Carlo numerical simulations of the correlations, which are in good agreement with the predicted analytical results.
Y1  - 2000
ER  - 
TY  - JOUR
A1  - Felbinger, Timo
A1  - Wilkens, Martin
T1  - Stochastic Wave-function Simulation of Two-time Correlation Functions
N2  - We propose an algorithm for the numerical simulation of two-time correlation functions by means of stochastic wave function. As a first application, we investigate the two-time correlation function of a nonlinear optical parametric oscillator.
Y1  - 1999
ER  - 
TY  - JOUR
A1  - Henkel, Carsten
A1  - Poetting, Sierk
A1  - Wilkens, Martin
T1  - Loss and heating of particles in small and noisy traps
N2  - We derive the time and loss rate for a trapped atom that is coupled to fluctuating fields in the vicinity of a room-temperature metallic and/or dielectric surface. Our results indicate a clear predominance of near-field effects over ordinary blackbody radiation. We develop a theoretical framework for both charged ions and neutral atoms with and without spin. Loss processes that are due to a transition to an untrapped internal state are included.
Y1  - 1999
ER  -