54 research outputs found
Quantum statistics and dynamics of nonlinear couplers with nonlinear exchange
In this paper we derive the quantum statistical and dynamical properties of
nonlinear optical couplers composed of two nonlinear waveguides operating by
the second subharmonic generation, which are coupled linearly through
evanescent waves and nonlinearly through nondegenerate optical parametric
interaction. Main attention is paid to generation and transmission of
nonclassical light, based on a discussion of squeezing phenomenon, normalized
second-order correlation function, and quasiprobability distribution functions.
Initially coherent, number and thermal states of optical beams are considered.
In particular, results are discussed in dependence on the strength of the
nonlinear coupling relatively to the linear coupling. We show that if the Fock
state enters the first waveguide and the vacuum state enters the
second waveguide, the coupler can serve as a generator of squeezed vacuum state
governed by the coupler parameters. Further, if thermal fields enter initially
the waveguides the coupler plays similar role as a microwave Josephson-junction
parametric amplifier to generate squeezed thermal light.Comment: 32 pages, 10 figure
Evolution of Fock states in three mixed harmonic oscillators: quantum statistics
In this communication we investigate the quantum statistics of three harmonic
oscillators mutually interacting with each other considering the modes are
initially in Fock states. After solving the equations of motion, the squeezing
phenomenon, sub-Poissonian statistics and quasiprobability functions are
discussed. We demonstrate that the interaction is able to produce squeezing of
different types. We show also that certain types of Fock states can evolve in
this interaction into thermal state and squeezed thermal state governed by the
interaction parameters.Comment: 25 pages, 7 figure
Controlling the quantum computational speed
The speed of quantum computation is investigated through the time evolution
of the speed of the orthogonality. The external field components for classical
treatment beside the detuning and the coupling parameters for quantum treatment
play important roles on the computational speed. It has been shown that the
number of photons has no significant effect on the speed of computation.
However, it is very sensitive to the variation in both detuning and the
interaction coupling parameters.Comment: 9 pages, 10 figure
Classical analysis of time behavior of radiation fields associated with biophoton signals
BACKGROUND: Propagation of photon signals in biological systems, such as neurons, accompanies the production of biophotons. The role of biophotons in a cell deserves special attention because it can be applied to diverse optical systems
Evolution of cat states in a dissipative parametric amplifier: decoherence and entanglement
The evolution of the Schr\"{o}dinger-cat states in a dissipative parametric
amplifier is examined. The main tool in the analysis is the normally ordered
characteristic function. Squeezing, photon-number distribution and reduced
factorial moments are discussed for the single- and compound-mode cases. Also
the single-mode Wigner function is demonstrated. In addition to the decoherence
resulting from the interaction with the environment (damped case) there are two
sources which can cause such decoherence in the system even if it is completely
isolated: these are the decay of the pump and the relative phases of the
initial cat states. Furthermore, for the damped case there are two regimes,
which are underdamped and overdamped. In the first (second) regime the signal
mode or the idler mode "collapses" to a statistical mixture (thermal field).Comment: 34 pages, 10 figure
Quantum properties of the parametric amplifier with and without pumping field fluctuations
The parametric amplifier with and without the pumping fluctuations of
coupling function is considered when the fields are initially prepared in
coherent light.
The pumping fluctuations are assumed to be normally distributed with
time-dependent variance. The effects of antibunching and anticorrelation of
photons on the photon distribution, correlation between modes and factorial
moments are demonstrated. A possible enhancement of photon antibunching for
certain values of initial mean photon numbers is shown and discussed. We have
shown also that new states (called modified squeezed vacuum states or even
thermal states) can be generated from such an interaction. Further, we have
demonstrated that the sum photon-number distribution can exhibit collapses and
revivals in the photon-number domain somewhat similar to those known in the
Jaynes-Cummings model.Comment: 17 pages, 6figure
Tripartite entanglement dynamics for atom in a two-mode nonlinear cavity
In this communication we introduce a new model which represents the
interaction between an atom and two fields injected simultaneously within a
cavity including the nonlinear couplers. By using the canonical transformation
the model can be regarded as a generalization of several well-known models. We
calculate and discuss entanglement between the tripartite system of one atom
and the two cavity modes. For a short interaction time, similarities between
the behavior based on our solution compared with the other simulation based on
a numerical linear algebra solution of the original Hamiltonian with truncated
Fock bases for each mode, is shown. For a specific value of the Kerr-like
medium defined in this letter, we find that the entanglement, as measured by
concurrence, may terminate abruptly in a finite time.Comment: 13 pages, 4 figure
The role of E1-E2 interplay in multiphonon Coulomb excitation
In this work we study the problem of a charged particle, bound in a
harmonic-oscillator potential, being excited by the Coulomb field from a fast
charged projectile. Based on a classical solution to the problem and using the
squeezed-state formalism we are able to treat exactly both dipole and
quadrupole Coulomb field components. Addressing various transition amplitudes
and processes of multiphonon excitation we study different aspects resulting
from the interplay between E1 and E2 fields, ranging from classical dynamic
polarization effects to questions of quantum interference. We compare exact
calculations with approximate methods. Results of this work and the formalism
we present can be useful in studies of nuclear reaction physics and in atomic
stopping theory.Comment: 10 pages, 6 figure
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