arXiv subjects

Przemyslaw Bienias

Publications and source records attributed to Przemyslaw Bienias.

42 records · Page 3Linked to original sources

arXiv2016

Quantum theory of Kerr nonlinearity with Rydberg slow light polaritons

We study the propagation of Rydberg slow light polaritons through an atomic medium for intermediate interactions. Then, the dispersion relation for the polaritons is well described by the slow light velocity alone, which allows for an analytical solution for arbitrary shape of the atomic cloud. We demonstrate the connection of Rydberg polaritons to the behavior of a conventional Kerr nonlinearity for weak interactions, and determine the leading quantum corrections for increasing interactions. We propose an experimental setup which allows one to measure the effective two-body interaction potential between slow light polaritons as well as higher body interactions.

quant-ph↗

arXiv2013

Ground state of a two component dipolar Fermi gas in a harmonic potential

Interacting two component Fermi gases are at the heart of our understanding of macroscopic quantum phenomena like superconductivity. Changing nature of the interaction is expected to head to novel quantum phases. Here we study the ground state of a two component fermionic gas in a harmonic potential with dipolar and contact interactions. Using a variational Wigner function we present the phase diagram of the system with equal but opposite values of the magnetic moment. We identify the second order phase transition from paramagnetic to ferronematic phase. Moreover, we show the impact of the experimentally relevant magnetic field on the stability and the magnetization of the system. We also investigate a two component Fermi gas with large but almost equal values of the magnetic moment to study how the interplay between contact and dipolar interactions affects the stability properties of the mixture. To be specific we discuss experimentally relevant parameters for ultracold $^{161}$Dy.

cond-mat.quant-gas↗

arXiv2013

Correlations of quasi-2D dipolar ultracold gas at finite temperatures

We study a quasi two dimensional dipolar gas at finite, but ultralow temperatures using the classical field approximation. The method, already used for a contact interacting gas, is extended here to samples with a weakly interacting long-range inter-atomic potential. We present statistical properties of the system for the current experiment with Chromium [Phys. Rev. A 84 053601 (2011)] and compare them with statistics for atoms with larger magnetic dipole moments. Significant enhancement of the third order correlation function, relevant for the particle losses, is found.

cond-mat.quant-gas↗

arXiv2012

Quasicondensation reexamined

We study in detail the effect of quasicondensation. We show that this effect is strictly related to dimensionality of the system. It is present in one dimensional systems independently of interactions - exists in repulsive, attractive or in non-interacting Bose gas in some range of temperatures below characteristic temperature of the quantum degeneracy. Based on this observation we analyze the quasicondensation in terms of a ratio of the two largest eigenvalues of the single particle density matrix for the ideal gas. We show that in the thermodynamic limit in higher dimensions the second largest eigenvalue vanishes (as compared to the first one) with total number of particles as $\simeq N^{-γ}$ whereas goes to zero only logarithmically in one dimension. We also study the effect of quasicondensation for various geometries of the system: from quasi-1D elongated one, through spherically symmetric 3D case to quasi-2D pancake-like geometry.

quant-ph↗

arXiv2011

Statistical properties of one dimensional attractive Bose gas

Using classical field approximation we present the first study of statistical properties of one dimensional Bose gas with attractive interaction. The canonical probability distribution is generated with the help of a Monte Carlo method. This way we obtain not only the depletion of the condensate with growing temperature but also its fluctuations. The most important is our discovery of a reduced coherence length, the phenomenon observed earlier only for the repulsive gas, known as quasicondensation.

quant-ph↗

arXiv2010

Statistical properties of one dimensional Bose gas

Monte Carlo method within, so called, classical fields approximation is applied to one dimensional weakly interacting repulsive Bose gas trapped in a harmonic potential. Equilibrium statistical properties of the condensate are calculated within a canonical ensemble. We also calculate experimentally relevant low order correlation functions of the whole gas.

quant-ph↗