493 research outputs found
Ultracold atomic Fermi-Bose mixtures in bichromatic optical dipole traps: a novel route to study fermion superfluidity
The study of low density, ultracold atomic Fermi gases is a promising avenue
to understand fermion superfluidity from first principles. One technique
currently used to bring Fermi gases in the degenerate regime is sympathetic
cooling through a reservoir made of an ultracold Bose gas. We discuss a
proposal for trapping and cooling of two-species Fermi-Bose mixtures into
optical dipole traps made from combinations of laser beams having two different
wavelengths. In these bichromatic traps it is possible, by a proper choice of
the relative laser powers, to selectively trap the two species in such a way
that fermions experience a stronger confinement than bosons. As a consequence,
a deep Fermi degeneracy can be reached having at the same time a softer
degenerate regime for the Bose gas. This leads to an increase in the
sympathetic cooling efficiency and allows for higher precision thermometry of
the Fermi-Bose mixture
Casimir force between eccentric cylinders
We consider the Casimir interaction between a cylinder and a hollow cylinder,
both conducting, with parallel axis and slightly different radii. The Casimir
force, which vanishes in the coaxial situation, is evaluated for both small and
large eccentricities using the proximity approximation. The cylindrical
configuration offers various experimental advantages with respect to the
parallel planes or the plane-sphere geometries, leading to favourable
conditions for the search of extra-gravitational forces in the micrometer range
and for the observation of finite temperature corrections.Comment: To be published in Europhysics Letters. 7 pages, 4 figure
Measurement-induced Squeezing of a Bose-Einstein Condensate
We discuss the dynamics of a Bose-Einstein condensate during its
nondestructive imaging. A generalized Lindblad superoperator in the condensate
master equation is used to include the effect of the measurement. A continuous
imaging with a sufficiently high laser intensity progressively drives the
quantum state of the condensate into number squeezed states. Observable
consequences of such a measurement-induced squeezing are discussed.Comment: 4 pages, 2 figures, submitted to PR
Uncertainty-principle noise in vacuum-tunneling transducers
The fundamental sources of noise in a vacuum-tunneling probe used as an
electromechanical transducer to monitor the location of a test mass are
examined using a first-quantization formalism. We show that a tunneling
transducer enforces the Heisenberg uncertainty principle for the position and
momentum of a test mass monitored by the transducer through the presence of two
sources of noise: the shot noise of the tunneling current and the momentum
fluctuations transferred by the tunneling electrons to the test mass. We
analyze a number of cases including symmetric and asymmetric rectangular
potential barriers and a barrier in which there is a constant electric field.
Practical configurations for reaching the quantum limit in measurements of the
position of macroscopic bodies with such a class of transducers are studied
Quantum dissipative effects in moving mirrors: a functional approach
We use a functional approach to study various aspects of the quantum
effective dynamics of moving, planar, dispersive mirrors, coupled to scalar or
Dirac fields, in different numbers of dimensions. We first compute the
Euclidean effective action, and use it to derive the imaginary part of the
`in-out' effective action. We also obtain, for the case of the real scalar
field in 1+1 dimensions, the Schwinger-Keldysh effective action and a
semiclassical Langevin equation that describes the motion of the mirror
including noise and dissipative effects due to its coupling to the quantum
fields.Comment: References added. Version to appear in Phys. Rev.
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
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
Exact Casimir interaction between eccentric cylinders
The Casimir force is the ultimate background in ongoing searches of
extra-gravitational forces in the micrometer range. Eccentric cylinders offer
favorable experimental conditions for such measurements as spurious
gravitational and electrostatic effects can be minimized. Here we report on the
evaluation of the exact Casimir interaction between perfectly conducting
eccentric cylinders using a mode summation technique, and study different
limiting cases of relevance for Casimir force measurements, with potential
implications for the understanding of mechanical properties of nanotubes.Comment: 5 pages, 4 figure
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