1,981 research outputs found
Sagnac Effect of Goedel's Universe
We present exact expressions for the Sagnac effect of Goedel's Universe. For
this purpose we first derive a formula for the Sagnac time delay along a
circular path in the presence of an arbitrary stationary metric in cylindrical
coordinates. We then apply this result to Goedel's metric for two different
experimental situations: First, the light source and the detector are at rest
relative to the matter generating the gravitational field. In this case we find
an expression that is formally equivalent to the familiar nonrelativistic
Sagnac time delay. Second, the light source and the detector are rotating
relative to the matter. Here we show that for a special rotation rate of the
detector the Sagnac time delay vanishes. Finally we propose a formulation of
the Sagnac time delay in terms of invariant physical quantities. We show that
this result is very close to the analogous formula of the Sagnac time delay of
a rotating coordinate system in Minkowski spacetime.Comment: 26 pages, including 4 figures, corrected typos, changed reference
Quantum reservoirs with ion chains
Ion chains are promising platforms for studying and simulating quantum
reservoirs. One interesting feature is that their vibrational modes can mediate
entanglement between two objects which are coupled through the vibrational
modes of the chain. In this work we analyse entanglement between the transverse
vibrations of two heavy impurity defects embedded in an ion chain, which is
generated by the coupling with the chain vibrations. We verify general scaling
properties of the defects dynamics and demonstrate that entanglement between
the defects can be a stationary feature of these dynamics. We then analyse
entanglement in chains composed of tens of ions and propose a measurement
scheme which allows one to verify the existence of the predicted entangled
state.Comment: 14 pages, 12 figure
Phase-dependent light propagation in atomic vapors
Light propagation in an atomic medium whose coupled electronic levels form a
diamond-configuration exhibits a critical dependence on the input conditions.
In particular, the relative phase of the input fields gives rise to
interference phenomena in the electronic excitation whose interplay with
relaxation processes determines the stationary state. We integrate numerically
the Maxwell-Bloch equations and observe two metastable behaviors for the
relative phase of the propagating fields corresponding to two possible
interference phenomena. These phenomena are associated to separate types of
response along propagation, minimize dissipation, and are due to atomic
coherence. These behaviors could be studied in gases of isotopes of
alkali-earth atoms with zero nuclear spin, and offer new perspectives in
control techniques in quantum electronics.Comment: 16 pages, 11 figures, v2: typos corrected, v3: final version, to
appear in Phys. Rev.
New frontiers at the interface of general relativity and quantum optics
In the present paper we follow three major themes: (i) concepts of rotation in general relativity, (ii) effects induced by these generalized rotations, and (iii) their measurement using interferometry. Our journey takes us from the Foucault pendulum via the Sagnac interferometer to manifestations of gravito-magnetism in double binary pulsars and in Gödel\u27s Universe. Throughout our article we emphasize the emerging role of matter wave interferometry based on cold atoms or Bose-Einstein condensates leading to superior inertial sensors. In particular, we advertise recent activities directed towards the operation of a coherent matter wave interferometer in an extended free fall. © 2009 Springer Science+Business Media B.V
Enhanced frequency up-conversion in Rb vapor
We demonstrate highly efficient generation of coherent 420nm light via
up-conversion of near-infrared lasers in a hot rubidium vapor cell. By
optimizing pump polarizations and frequencies we achieve a single-pass
conversion efficiency of 260% per Watt, significantly higher than in previous
experiments. A full exploration of the coherent light generation and
fluorescence as a function of both pump frequencies reveals that coherent blue
light is generated close to 85Rb two-photon resonances, as predicted by theory,
but at high vapor pressure is suppressed in spectral regions that do not
support phase matching or exhibit single-photon Kerr refraction. Favorable
scaling of our current 1mW blue beam power with additional pump power is
predicted.Comment: 6 pages, 4 figures. Modified to include referees' improvement
Dropping cold quantum gases on Earth over long times and large distances
We describe the non-relativistic time evolution of an ultra-cold degenerate
quantum gas (bosons/fermions) falling in Earth's gravity during long times (10
sec) and over large distances (100 m). This models a drop tower experiment that
is currently performed by the QUANTUS collaboration at ZARM (Bremen, Germany).
Starting from the classical mechanics of the drop capsule and a single particle
trapped within, we develop the quantum field theoretical description for this
experimental situation in an inertial frame, the corotating frame of the Earth,
as well as the comoving frame of the drop capsule. Suitable transformations
eliminate non-inertial forces, provided all external potentials (trap, gravity)
can be approximated with a second order Taylor expansion around the
instantaneous trap center. This is an excellent assumption and the harmonic
potential theorem applies. As an application, we study the quantum dynamics of
a cigar-shaped Bose-Einstein condensate in the Gross-Pitaevskii mean-field
approximation. Due to the instantaneous transformation to the rest-frame of the
superfluid wave packet, the long-distance drop (100m) can be studied easily on
a numerical grid.Comment: 18 pages latex, 5 eps figures, submitte
General relativistic Sagnac formula revised
The Sagnac effect is a time or phase shift observed between two beams of
light traveling in opposite directions in a rotating interferometer. We show
that the standard description of this effect within the framework of general
relativity misses the effect of deflection of light due to rotational inertial
forces. We derive the necessary modification and demonstrate it through a
detailed analysis of the square Sagnac interferometer rotating about its
symmetry axis in Minkowski space-time. The role of the time shift in a Sagnac
interferometer in the synchronization procedure of remote clocks as well as its
analogy with the Aharanov-Bohm effect are revised.Comment: 11 pages, 3 figure
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