Cooling dynamics of ultracold two-species Fermi-Bose mixtures

We compare strategies for evaporative and sympathetic cooling of two-species Fermi-Bose mixtures in single-color and two-color optical dipole traps. We show that in the latter case a large heat capacity of the bosonic species can be maintained during the entire cooling process. This could allow to efficiently achieve a deep Fermi degeneracy regime having at the same time a significant thermal fraction for the Bose gas, crucial for a precise thermometry of the mixture. Two possible signatures of a superfluid phase transition for the Fermi species are discussed.Comment: 4 pages, 3 figure

Development of an apparatus for cooling 6Li-87Rb Fermi-Bose mixtures in a light-assisted magnetic trap

We describe an experimental setup designed to produce ultracold trapped gas clouds of fermionic 6Li and bosonic 87Rb. This combination of alkali metals has the potential to reach deeper Fermi degeneracy with respect to other mixtures since it allows for improved heat capacity matching which optimizes sympathetic cooling efficiency. Atomic beams of the two species are independently produced and then decelerated by Zeeman slowers. The slowed atoms are collected into a magneto-optical trap and then transferred into a quadrupole magnetic trap. An ultracold Fermi gas with temperature in the 10^-3 T_F range should be attainable through selective confinement of the two species via a properly detuned laser beam focused in the center of the magnetic trap.Comment: Presented at LPHYS'06, 8 figure

Photon creation in a spherical oscillating cavity

We study the photon creation inside a perfectly conducting, spherical oscillating cavity. The electromagnetic field inside the cavity is described by means of two scalar fields which satisfy Dirichlet and (generalized) Neumann boundary conditions. As a preliminary step, we analyze the dynamical Casimir effect for both scalar fields. We then consider the full electromagnetic case. The conservation of angular momentum of the electromagnetic field is also discussed, showing that photons inside the cavity are created in singlet states.Comment: 14 pages, no figure

Anomalies in electrostatic calibrations for the measurement of the Casimir force in a sphere-plane geometry

We have performed precision electrostatic calibrations in the sphere-plane geometry and observed anomalous behavior. Namely, the scaling exponent of the electrostatic signal with distance was found to be smaller than expected on the basis of the pure Coulombian contribution and the residual potential found to be distance dependent. We argue that these findings affect the accuracy of the electrostatic calibrations and invite reanalysis of previous determinations of the Casimir force.Comment: 4 pages, 4 figure

Are violations to temporal Bell inequalities there when somebody looks?

The possibility of observing violations of temporal Bell inequalities, originally proposed by Leggett as a mean of testing the quantum mechanical delocalization of suitably chosen macroscopic bodies, is discussed by taking into account the effect of the measurement process. A general criterion quantifying this possibility is defined and shown not to be fulfilled by the various experimental configurations proposed so far to test inequalities of different forms.Comment: 7 pages, 1 eps figure, needs europhys.sty and euromacr.tex, enclosed in the .tar.gz file; accepted for publication in Europhysics Letter

Thermal and dissipative effects in Casimir physics

We report on current efforts to detect the thermal and dissipative contributions to the Casimir force. For the thermal component, two experiments are in progress at Dartmouth and at the Institute Laue Langevin in Grenoble. The first experiment will seek to detect the Casimir force at the largest explorable distance using a cylinder-plane geometry which offers various advantages with respect to both sphere-plane and parallel-plane geometries. In the second experiment, the Casimir force in the parallel-plane configuration is measured with a dedicated torsional balance, up to 10 micrometers. Parallelism of large surfaces, critical in this configuration, is maintained through the use of inclinometer technology already implemented at Grenoble for the study of gravitationally bound states of ultracold neutrons, For the dissipative component of the Casimir force, we discuss detection techniques based upon the use of hyperfine spectroscopy of ultracold atoms and Rydberg atoms. Although quite challenging, this triad of experimental efforts, if successful, will give us a better knowledge of the interplay between quantum and thermal fluctuations of the electromagnetic field and of the nature of dissipation induced by the motion of objects in a quantum vacuum.Comment: Contribution to QFEXT'06, appeared in special issue of Journal of Physics

Impulsive quantum measurements: restricted path integral versus von Neumann collapse

The relation between the restricted path integral approach to quantum measurement theory and the commonly accepted von Neumann wavefunction collapse postulate is presented. It is argued that in the limit of impulsive measurements the two approaches lead to the same predictions. The example of repeated impulsive quantum measurements of position performed on a harmonic oscillator is discussed in detail and the quantum nondemolition strategies are recovered in both the approaches.Comment: 12 pages, 3 figure

Quantum damping of position due to energy measurements

Quantum theory for measurements of energy is introduced and its consequences for the average position of monitored dynamical systems are analyzed. It turns out that energy measurements lead to a localization of the expectation values of other observables. This is manifested, in the case of position, as a damping of the motion without classical analogue. Quantum damping of position for an atom bouncing on a reflecting surface in presence of a homogeneous gravitational field is dealt in detail and the connection with an experiment already performed in the classical regime is studied. We show that quantum damping is testable provided that the same measurement strength obtained in the experimental verification of the quantum Zeno effect in atomic spectroscopy [W. M. Itano et al., Phys. Rev. A {\bf 41}, 2295 (1990)] is made available.Comment: 19 pages + 4 figures available upon request; Plain REVTeX; To be published in Phys. Rev.

Vortex Nucleation in a Stirred Bose-Einstein Condensate

We studied the nucleation of vortices in a Bose-Einstein condensate stirred by a laser beam. We observed the vortex cores using time-of-flight absorption imaging. By varying the size of the stirrer, we observed either discrete resonances or a broad response as a function of the frequency of the stirrer's motion. Stirring beams small compared to the condensate size generated vortices below the critical rotation frequency for the nucleation of surface modes, suggesting a local mechanism of generation. In addition, we observed the centrifugal distortion of the condensate due to the rotating vortex lattice and found evidence for bent vortices