14,136 research outputs found
The CWKB approach to non-reflecting potential and cosmological implications
We discuss the method of calculating the reflection coefficient using complex
trajectory WKB (CWKB) approximation. This enables us to give an interpretation
of non-reflecting nature of the potential under certain conditions and clarify
some points, reported incorrectly elsewhere [vs:ejp] for the potential
. We show that the repeated reflectios between the
turning points are essential, which most authors overlooked, in obtaining the
non-reflecting c ondition. We find that the considered repeated reflection
paths are in conformity with Bogolubov transformation technique. We discuss the
implications of the results when applied to the particle production scenario,
considering as a time variable and also stress the cosmological
implications of the result with reference to radiation domonated and de Sitter
spacetime.Comment: 9 pages, late
Nonclassicality and decoherence of photon-subtracted squeezed states
We discuss nonclassical properties of single-photon subtracted squeezed
vacuum states in terms of the sub-Poissonian statistics and the negativity of
the Wigner function. We derive a compact expression for the Wigner function
from which we find the region of phase space where Wigner function is negative.
We find an upper bound on the squeezing parameter for the state to exhibit
sub-Poissonian statistics. We then study the effect of decoherence on the
single-photon subtracted squeezed states. We present results for two different
models of decoherence, viz. amplitude decay model and the phase diffusion
model. In each case we give analytical results for the time evolution of the
state. We discuss the loss of nonclassicality as a result of decoherence. We
show through the study of their phase-space properties how these states decay
to vacuum due to the decay of photons. We show that phase damping leads to very
slow decoherence than the photon-number decay.Comment: Figures are in GIF format separately, submitte
Transfer of an unknown quantum state, quantum networks, and memory
We present a protocol for transfer of an unknown quantum state. The protocol
is based on a two-mode cavity interacting dispersively in a sequential manner
with three-level atoms in configuration. We propose a scheme for
quantum networking using an atomic channel. We investigate the effect of cavity
decoherence in the entire process. Further, we demonstrate the possibility of
an efficient quantum memory for arbitrary superposition of two modes of a
cavity contaning one photon.Comment: 5 pages, 4 figures, RevTeX4, Submitted to PR
Preparation of W, GHZ, and two-qutrit states using bimodal cavities
We show how one can prepare three-qubit entangled states like W states,
Greenberger-Horne-Zeilinger states as well as two-qutrit entangled states using
the multiatom two-mode entanglement. We propose a technique of preparing such a
multi-particle entanglement using stimulated Raman adiabatic passage. We
consider a collection of three-level atoms in configuration
simultaneously interacting with a resonant two-mode cavity for this purpose.
Our approach permits a variety of multiparticle extensions.Comment: 8 pages, 5 figures. J. Mod. Opt. (in press
Inseparability inequalities for higher-order moments for bipartite systems
There are several examples of bipartite entangled states of continuous
variables for which the existing criteria for entanglement using the
inequalities involving the second order moments are insufficient. We derive new
inequalities involving higher order correlation, for testing entanglement in
non-Gaussian states. In this context we study an example of a non-Gaussian
state, which is a bipartite entangled state of the form .
Our results open up an avenue to search for new inequalities to test
entanglement in non-Gaussian states.Comment: 7 pages, Submitte
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