304 research outputs found
The non-Abelian state-dependent gauge field in optics
The covariant formulation of the quantum dynamics in CP(1) should lead to the
observable geometrodynamical effects for the local dynamical variable of the
light polarization states.Comment: 8 pages, 3 figures, LaTe
Gravitational Phase Operator and Cosmic Strings
A quantum equivalence principle is formulated by means of a gravitational
phase operator which is an element of the Poincare group. This is applied to
the spinning cosmic string which suggests that it may (but not necessarily)
contain gravitational torsion. A new exact solution of the Einstein-
Cartan-Sciama-Kibble equations for the gravitational field with torsion is
obtained everywhere for a cosmic string with uniform energy density, spin
density and flux. A novel effect due to the quantized gravitational field of
the cosmic string on the wave function of a particle outside the string is used
to argue that spacetime points are not meaningful in quantum gravity.Comment: 22 pages, to be published Phys. Rev. D. Some minor changes have been
made and a reference has been added to the paper of D.V. Gal'tsov and P.S.
Letelier, Phys. Rev. D 47 (1993) 4273, which first contained the metric (2.2)
external to the cosmic string. The present paper extends this solution to a
regular solution inside the string as wel
Testing Bell's inequality using Aharonov-Casher effect
We propose the Aharonov-Casher (AC) effect for four entangled spin-half
particles carrying magnetic moments in the presence of impenetrable line
charge. The four particle state undergoes AC phase shift in two causually
disconnected region which can show up in the correlations between different
spin states of distant particles. This correlation can violate Bell's
inequality, thus displaying the non-locality for four particle entangled states
in an objective way. Also, we have suggested how to control the AC phase shift
locally at two distant locations to test Bell's inequality. We belive that
although the single particle AC effect may not be non-local but the entangled
state AC effect is a non-local one.Comment: Latex, 6 pages, no figures, submitted to Phys. Rev.
An adaptive moments estimation technique applied to MST radar echoes
An adaptive spectral moments estimation technique has been developed for analyzing the Doppler spectra of the mesosphere-stratosphere-troposphere (MST) radar signals. The technique, implemented with the MST radar at Gadanki (13.5°N, 79°E), is based on certain criteria, set up for the Doppler window, signal-to-noise ratio (SNR), and wind shear parameters, which are used to adaptively track the signal in the range-Doppler spectral frame. Two cases of radar data, one for low and the other for high SNR conditions, have been analyzed and the results are compared with those from the conventional method based on the strongest peak detection in each range gate. The results clearly demonstrate that by using the adaptive method the height coverage can be considerably enhanced compared to the conventional method. For the low SNR case, the height coverage for the adaptive and conventional methods is about 22 and 11 km, respectively; the corresponding heights for the high SNR case are 24 and 13 km. To validate the results obtained through the adaptive method, the velocity profile is compared with global positioning system balloon sounding (GPS sonde) observations. The results of the adaptive method show excellent agreement with the GPS sonde measured wind speeds and directions throughout the height profile. To check the robustness and reliability of the adaptive algorithm, data taken over a diurnal cycle at 1-h intervals were analyzed. The results demonstrate the reliability of the algorithm in extracting wind profiles that are self-consistent in time. The adaptive method is thus found to be of considerable advantage over the conventional method in extracting information from the MST radar signal spectrum, particularly under low SNR conditions that are free from interference and ground clutter
Quantum Phase Shift in Chern-Simons Modified Gravity
Using a unified approach of optical-mechanical analogy in a semiclassical
formula, we evaluate the effect of Chern-Simons modified gravity on the quantum
phase shift of de Broglie waves in neutron interferometry. The phase shift
calculated here reveals, in a single equation, a combination of effects coming
from Newtonian gravity, inertial forces, Schwarzschild and Chern-Simons
modified gravity. However the last two effects, though new, turn out to be too
tiny to be observed, and hence only of academic interest at present. The
approximations, wherever used, as well as the drawbacks of the non-dynamical
approach are clearly indicated.Comment: 16 pages, minor errors corrected. Accepted for publication in Phys.
Rev.
On a generalized gravitational Aharonov-Bohm effect
A massless spinor particle is considered in the background gravitational
field due to a rotating body. In the weak field approximation it is shown that
the solution of the Weyl equations depend on the angular momentum of the
rotating body, which does not affect the curvature in this approximation. This
result may be looked upon as a generalization of the gravitational
Aharonov-Bohm effect.Comment: 10 pages, LATEX fil
Parallel transport in an entangled ring
This paper defines a notion of parallel transport in a lattice of quantum
particles, such that the transformation associated with each link of the
lattice is determined by the quantum state of the two particles joined by that
link. We focus particularly on a one-dimensional lattice--a ring--of entangled
rebits, which are binary quantum objects confined to a real state space. We
consider states of the ring that maximize the correlation between nearest
neighbors, and show that some correlation must be sacrificed in order to have
non-trivial parallel transport around the ring. An analogy is made with lattice
gauge theory, in which non-trivial parallel transport around closed loops is
associated with a reduction in the probability of the field configuration. We
discuss the possibility of extending our result to qubits and to higher
dimensional lattices.Comment: 31 pages, no figures; v2 includes a new example of a qubit rin
Bures and Statistical Distance for Squeezed Thermal States
We compute the Bures distance between two thermal squeezed states and deduce
the Statistical Distance metric. By computing the curvature of this metric we
can identify regions of parameter space most sensitive to changes in these
parameters and thus lead to optimum detection statistics.Comment: 15 pages, 1 figure (not included - obtain from Author) To appear in
Journal of Physics
Mass dependence of the gravitationally-induced wave-function phase
The leading mass dependence of the wave function phase is calculated in the
presence of gravitational interactions. The conditions under which this phase
contains terms depending on both the square of the mass and the gravitational
constant are determined. The observability of such terms is briefly discussed.Comment: 5 pages, no figures, requires Revtex. The discussion has been
extended and clarifie
General Relativistic Thermoelectric Effects in Superconductors
We discuss the general-relativistic contributions to occur in the
electromagnetic properties of a superconductor with a heat flow. The appearance
of general-relativistic contribution to the magnetic flux through a
superconducting thermoelectric bimetallic circuit is shown. A response of the
Josephson junctions to a heat flow is investigated in the general-relativistic
framework. Some gravitothermoelectric effects which are observable in the
superconducting state in the Earth's gravitational field are considered.Comment: 13 pages, 2 figure
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