Coherent scattering of a Multiphoton Quantum Superposition by a Mirror-BEC

We present the proposition of an experiment in which the multiphoton quantum superposition consisting of N= 10^5 particles generated by a quantum-injected optical parametric amplifier (QI-OPA), seeded by a single-photon belonging to an EPR entangled pair, is made to interact with a Mirror-BEC shaped as a Bragg interference structure. The overall process will realize a Macroscopic Quantum Superposition (MQS) involving a microscopic single-photon state of polarization entangled with the coherent macroscopic transfer of momentum to the BEC structure, acting in space-like separated distant places.Comment: 4 pages, 4 figure

Dynamical instabilities of Bose-Einstein condensates at the band-edge in one-dimensional optical lattices

We report on experiments that demonstrate dynamical instability in a Bose-Einstein condensate at the band-edge of a one-dimensional optical lattice. The instability manifests as rapid depletion of the condensate and conversion to a thermal cloud. We consider the collisional processes that can occur in such a system, and perform numerical modeling of the experiments using both a mean-field and beyond mean-field approach. We compare our numerical results to the experimental data, and find that the Gross-Pitaevskii equation is not able to describe this experiment. Our beyond mean-field approach, known as the truncated Wigner method, allows us to make quantitative predictions for the processes of parametric growth and thermalization that are observed in the laboratory, and we find good agreement with the experimental results.Comment: v2: Added several reference

Quantum theory of a polarization phase-gate in an atomic tripod configuration

We present the quantum theory of a polarization phase-gate that can be realized in a sample of ultracold rubidium atoms driven into a tripod configuration. The main advantages of this scheme are in its relative simplicity and inherent symmetry. It is shown that the conditional phase shifts of order $\pi$ can be attained.Comment: X International Conference on Quantum Optics, Minsk, Belaru

Ergodicity in randomly perturbed quantum systems

The theoretical cornerstone of statistical mechanics is the ergodic assumption that all accessible configurations of a physical system are equally likely. Here we show how such property arises when an open quantum system is continuously perturbed by an external environment effectively observing the system at random times while the system dynamics approaches the quantum Zeno regime. In this context, by large deviation theory we analytically show how the most probable value of the probability for the system to be in a given state eventually deviates from the non-stochastic case when the Zeno condition is not satisfied. We experimentally test our results with ultra-cold atoms prepared on an atom chip.Comment: 6 pages, 5 figure

Laser ablation in liquid media of noble metals. The physics of plasma plume and the optical properties of the produced colloids

In experiments of pulsed laser ablation in liquids (PLAL), performed on noble metal targets, many physical aspects regarding the characteristics of the plasma plume generated in the confining liquid, and the optical properties of the produced nanocolloids deserve a clear definition and discussion. In this paper we present the relevant theories and the results of experiments performed in our laboratory on this argument

Loss of superfluidity in a Bose-Einstein condensate via forced resonant oscillations

We predict the loss of superfluidity in a Bose-Einstein condensate in an axially symmetric harmonic trap alone during resonant collective oscillations via a classical dynamical transition. The forced resonant oscillation can be initiated by (a) a periodic modulation of the atomic scattering length with a frequency that equals twice the radial trapping frequency or multiples thereof, or by (b) a periodic modulation of the radial trapping potential with a frequency that equals the radial trapping frequency or multiples thereof. Suggestion for future experiment is made.Comment: 12 Latex Pages, 12 eps figures, Accepted in Physics Letters

Superradiant light scattering from a moving Bose-Einstein condensate

We investigate the interaction of a moving BEC with a far detuned laser beam. Superradiant Rayleigh scattering arises from the spontaneous formation of a matter-wave grating due to the interference of two wavepackets with different momenta. The system is described by the CARL-BEC model which is a generalization of the Gross-Pitaevskii model to include the self-consistent evolution of the scattered field. The experiment gives evidence of a damping of the matter-wave grating which depends on the initial velocity of the condensate. We describe this damping in terms of a phase-diffusion decoherence process, in good agreement with the experimental results