83 research outputs found
Analytical operator solution of master equations describing phase-sensitive processes
We present a method of solving master equations which may describe, in their
most general form, phase sensitive processes such as decay and amplification.
We make use of the superoperator technique.Comment: 10 pages, LaTex, 3 figures, accepted for publication in International
Journal of Modern Physics
Optical realization of nonlinear quantum dynamics
In a cavity filled with a Kerr medium it is possible to generate the
superposition of coherent states, i.e. Schroodinger cat states may be realized
in this system. We show that such a medium may be mimicked by the propagation
of a conveniently shaped Gaussian beam in a GRIN device. This is attained by
introducing a second order correction to the paraxial propagation of the beam.
An additional result is that a Gaussian beam propagating in GRIN media, may
split into two Gaussian beams
Entanglement between motional states of a single trapped ion and light
We propose a generation method of Bell-type states involving light and the
vibrational motion of a single trapped ion. The trap itself is supposed to be
placed inside a high- cavity sustaining a single mode, quantized
electromagnetic field. Entangled light-motional states may be readily generated
if a conditional measurement of the ion's internal electronic state is made
after an appropriate interaction time and a suitable preparation of the initial
state. We show that all four Bell states may be generated using different
motional sidebands (either blue or red), as well as adequate ionic relative
phases.Comment: 4 pages, LaTe
Recovering coherence from decoherence: a method of quantum state reconstruction
We present a feasible scheme for reconstructing the quantum state of a field
prepared inside a lossy cavity. Quantum coherences are normally destroyed by
dissipation, but we show that at zero temperature we are able to retrieve
enough information about the initial state, making possible to recover its
Wigner function as well as other quasiprobabilities. We provide a numerical
simulation of a Schroedinger cat state reconstruction.Comment: 8 pages, in RevTeX, 4 figures, accepted for publication in Phys. Rev.
A (november 1999
Cauchy-Riemann beams
By using operator techniques, we solve the paraxial wave equation for a field
given by the multiplication of a Gaussian function and an entire function. The
latter possesses a unique property, being an eigenfunction of the {\it
perpendicular} Laplacian with a zero eigenvalue, a consequence of the
Cauchy-Riemann equations. We demonstrate, both theoretically and
experimentally, the inherent rotation of this field during its propagation. The
explanation for these rotations lies in the utilization of the quantum (Bohm)
potential. The simplicity of this outcome reveals promising prospects: it
enables the analytical deduction of the Fraunhofer or Fresnel diffraction
pattern. In essence, this means that obtaining the Fresnel or Fourier transform
of a function satisfying the Cauchy-Riemann equations becomes a straightforward
task
States interpolating between number and coherent states and their interaction with atomic systems
Using the eigenvalue definition of binomial states we construct new
intermediate number-coherent states which reduce to number and coherent states
in two different limits. We reveal the connection of these intermediate states
with photon-added coherent states and investigate their non-classical
properties and quasi-probability distributions in detail. It is of interest to
note that these new states, which interpolate between coherent states and
number states, neither of which exhibit squeezing, are nevertheless squeezed
states. A scheme to produce these states is proposed. We also study the
interaction of these states with atomic systems in the framework of the
two-photon Jaynes-Cummings model, and describe the response of the atomic
system as it varies between the pure Rabi oscillation and the collapse-revival
mode and investigate field observables such as photon number distribution,
entropy and the Q-function.Comment: 26 pages, 29 EPS figures, Latex, Accepted for publication in J.Phys.
Symplectic evolution of Wigner functions in markovian open systems
The Wigner function is known to evolve classically under the exclusive action
of a quadratic hamiltonian. If the system does interact with the environment
through Lindblad operators that are linear functions of position and momentum,
we show that the general evolution is the convolution of the classically
evolving Wigner function with a phase space gaussian that broadens in time. We
analyze the three generic cases of elliptic, hyperbolic and parabolic
Hamiltonians. The Wigner function always becomes positive in a definite time,
which is shortest in the hyperbolic case. We also derive an exact formula for
the evolving linear entropy as the average of a narrowing gaussian taken over a
probability distribution that depends only on the initial state. This leads to
a long time asymptotic formula for the growth of linear entropy.Comment: this new version treats the dissipative cas
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