51 research outputs found
On the Phenomenology of Tachyon Radiation
We present a brief overview of the different kinds of electromagnetic
radiations expected to come from (or to be induced by) space-like sources
(tachyons). New domains of radiation are here considered; and the possibility
of experimental observation of tachyons via electromagnetic radiation is
discussed
Internal decoherence in nano-object interferometry due to phonons
We discuss the coherent splitting and recombining of a nanoparticle in a
mesoscopic "closed-loop" Stern-Gerlach interferometer in which the observable
is the spin of a single impurity embedded in the particle. This spin, when
interacting with a pulsed magnetic gradient, generates the force on the
particle. We calculate the internal decoherence which arises as the displaced
impurity excites internal degrees of freedom (phonons) that may provide Welcher
Weg information and preclude interference. We estimate the constraints this
decoherence channel puts on future interference experiments with massive
objects. We find that for a wide range of masses, forces and temperatures,
phonons do not inhibit Stern-Gerlach interferometry with micro-scale objects.
However, phonons do constitute a fundamental limit on the splitting of larger
macroscopic objects if the applied force induces phonons.Comment: 10 pages, 6 figures, submitted to Festschrift in honor of Nobel prize
awarded to R. Penros
Fundamental Limits for Coherent Manipulation on Atom Chips
The limitations for the coherent manipulation of neutral atoms with
fabricated solid state devices, so-called `atom chips', are addressed.
Specifically, we examine the dominant decoherence mechanism, which is due to
the magnetic noise originating from the surface of the atom chip. It is shown
that the contribution of fluctuations in the chip wires at the shot noise level
is not negligible. We estimate the coherence times and discuss ways to increase
them. Our main conclusion is that future advances should allow for coherence
times as long as one second, a few micrometers away from the surface.Comment: selected papers of the DPG spring meeting `Quantum Optics'
(Osnabrueck, Germany, 4-8 march 2002), submitted to Applied Physics
Robust spatial coherence 5m from a room-temperature atom chip
We study spatial coherence near a classical environment by loading a
Bose-Einstein condensate into a magnetic lattice potential and observing
diffraction. Even very close to a surface (5m), and even when the
surface is at room temperature, spatial coherence persists for a relatively
long time (500ms). In addition, the observed spatial coherence extends
over several lattice sites, a significantly greater distance than the
atom-surface separation. This opens the door for atomic circuits, and may help
elucidate the interplay between spatial dephasing, inter-atomic interactions,
and external noise.Comment: 15 pages, 14 figures, revised for final publication. This manuscript
includes in-depth analysis of the data presented in arXiv:1502.0160
One-mirror Fabry-Perot and one-slit Young interferometry
We describe a new and distinctive interferometry in which a probe particle
scatters off a superposition of locations of a single free target particle. In
one dimension, probe particles incident on superposed locations of a single
"mirror" can interfere as if in a Fabry-Perot interferometer; in two
dimensions, probe particles scattering off superposed locations of a single
"slit" can interfere as if in a two-slit Young interferometer. The condition
for interference is loss of orthogonality of the target states and reduces, in
simple examples, to transfer of orthogonality from target to probe states. We
analyze experimental parameters and conditions necessary for interference to be
observed.Comment: 5 pages, 2 figures, RevTeX, submitted to PR
Suppression and enhancement of decoherence in an atomic Josephson junction
We examine the role of interactions for a Bose gas trapped in a double-well
potential ("Bose-Josephson junction") when external noise is applied and the
system is initially delocalized with equal probability amplitudes in both
sites. The noise may have two kinds of effects: loss of atoms from the trap,
and random shifts in the relative phase or number difference between the two
wells. The effects of phase noise are mitigated by atom-atom interactions and
tunneling, such that the dephasing rate may be reduced to half its single-atom
value. Decoherence due to number noise (which induces fluctuations in the
relative atom number between the wells) is considerably enhanced by the
interactions. A similar scenario is predicted for the case of atom loss, even
if the loss rates from the two sites are equal. In fact, interactions convert
the increased uncertainty in atom number (difference) into (relative) phase
diffusion and reduce the coherence across the junction. We examine the
parameters relevant for these effects using a simple model of the trapping
potential based on an atom chip device. These results provide a framework for
mapping the dynamical range of barriers engineered for specific applications
and sets the stage for more complex circuits ("atomtronics")
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