1,014 research outputs found
Squeezing and photon distribution in a vibrating cavity
We obtain explicit analytical expressions for the quadrature variances and
the photon distribution functions of the electromagnetic field modes excited
from vacuum or thermal states due to the non-stationary Casimir effect in an
ideal one-dimensional Fabry--Perot cavity with vibrating walls, provided the
frequency of vibrations is close to a multiple frequency of the fundamental
unperturbed electromagnetic mode.Comment: 20 pages, LaTex2e, iopart document class, 2 ps figures, accepted for
publication in J. Phys.
Justification of the symmetric damping model of the dynamical Casimir effect in a cavity with a semiconductor mirror
A "microscopic" justification of the "symmetric damping" model of a quantum
oscillator with time-dependent frequency and time-dependent damping is given.
This model is used to predict results of experiments on simulating the
dynamical Casimir effect in a cavity with a photo-excited semiconductor mirror.
It is shown that the most general bilinear time-dependent coupling of a
selected oscillator (field mode) to a bath of harmonic oscillators results in
two equal friction coefficients for the both quadratures, provided all the
coupling coefficients are proportional to a single arbitrary function of time
whose duration is much shorter than the periods of all oscillators. The choice
of coupling in the rotating wave approximation form leads to the "mimimum
noise" model of the quantum damped oscillator, introduced earlier in a pure
phenomenological way.Comment: 9 pages, typos corrected, corresponds to the published version,
except for the reference styl
Decoherence and thermalization dynamics of a quantum oscillator
We introduce the quantitative measures characterizing the rates of
decoherence and thermalization of quantum systems. We study the time evolution
of these measures in the case of a quantum harmonic oscillator whose relaxation
is described in the framework of the standard master equation, for various
initial states (coherent, `cat', squeezed and number). We establish the
conditions under which the true decoherence measure can be approximated by the
linear entropy . We show that at low temperatures and for
highly excited initial states the decoherence process consists of three
distinct stages with quite different time scales. In particular, the `cat'
states preserve 50% of the initial coherence for a long time interval which
increases logarithmically with increase of the initial energy.Comment: 24 pages, LaTex, 8 ps figures, accepted for publication in J. Opt.
Time dependent nonclassical properties of even and odd nonlinear coherent states
We construct even and odd nonlinear coherent states of a parametric
oscillator and examine their nonclassical properties.It has been shown that
these superpositions exhibit squeezing and photon antibunching which change
with time.Comment: 3 eps figure
Numerical approach to the dynamical Casimir effect
The dynamical Casimir effect for a massless scalar field in 1+1-dimensions is
studied numerically by solving a system of coupled first-order differential
equations. The number of scalar particles created from vacuum is given by the
solutions to this system which can be found by means of standard numerics. The
formalism already used in a former work is derived in detail and is applied to
resonant as well as off-resonant cavity oscillations.Comment: 15 pages, 4 figures, accepted for publication in J. Phys. A (special
issue: Proceedings of QFEXT05, Barcelona, Sept. 5-9, 2005
Engineering Quantum Jump Superoperators for Single Photon Detectors
We study the back-action of a single photon detector on the electromagnetic
field upon a photodetection by considering a microscopic model in which the
detector is constituted of a sensor and an amplification mechanism. Using the
quantum trajectories approach we determine the Quantum Jump Superoperator (QJS)
that describes the action of the detector on the field state immediately after
the photocount. The resulting QJS consists of two parts: the bright counts
term, representing the real photoabsorptions, and the dark counts term,
representing the amplification of intrinsic excitations inside the detector.
First we compare our results for the counting rates to experimental data,
showing a good agreement. Then we point out that by modifying the field
frequency one can engineer the form of QJS, obtaining the QJS's proposed
previously in an ad hoc manner
Vibrating Cavities - A numerical approach
We present a general formalism allowing for efficient numerical calculation
of the production of massless scalar particles from vacuum in a one-dimensional
dynamical cavity, i.e. the dynamical Casimir effect. By introducing a
particular parametrization for the time evolution of the field modes inside the
cavity we derive a coupled system of first-order linear differential equations.
The solutions to this system determine the number of created particles and can
be found by means of numerical methods for arbitrary motions of the walls of
the cavity. To demonstrate the method which accounts for the intermode coupling
we investigate the creation of massless scalar particles in a one-dimensional
vibrating cavity by means of three particular cavity motions. We compare the
numerical results with analytical predictions as well as a different numerical
approach.Comment: 28 pages, 19 figures, accepted for publication in J. Opt. B: Quantum
Semiclass. Op
Properties of Squeezed-State Excitations
The photon distribution function of a discrete series of excitations of
squeezed coherent states is given explicitly in terms of Hermite polynomials of
two variables. The Wigner and the coherent-state quasiprobabilities are also
presented in closed form through the Hermite polynomials and their limiting
cases. Expectation values of photon numbers and their dispersion are
calculated. Some three-dimensional plots of photon distributions for different
squeezing parameters demonstrating oscillatory behaviour are given.Comment: Latex,35 pages,submitted to Quant.Semiclassical Op
The Schrodinger particle in an oscillating spherical cavity
We study a Schrodinger particle in an infinite spherical well with an
oscillating wall. Parametric resonances emerge when the oscillation frequency
is equal to the energy difference between two eigenstates of the static cavity.
Whereas an analytic calculation based on a two-level system approximation
reproduces the numerical results at low driving amplitudes, epsilon, we observe
a drastic change of behaviour when epsilon > 0.1, when new resonance states
appear bearing no apparent relation to the eigenstates of the static system.Comment: 9 pages, 6 figures, corrected typo
Resonant photon creation in a three dimensional oscillating cavity
We analyze the problem of photon creation inside a perfectly conducting,
rectangular, three dimensional cavity with one oscillating wall. For some
particular values of the frequency of the oscillations the system is resonant.
We solve the field equation using multiple scale analysis and show that the
total number of photons inside the cavity grows exponentially in time. This is
also the case for slightly off-resonance situations. Although the spectrum of a
cavity is in general non equidistant, we show that the modes of the
electromagnetic field can be coupled, and that the rate of photon creation
strongly depends on this coupling. We also analyze the thermal enhancement of
the photon creation.Comment: 13 pages. New section on off-resonance motion is included. To appear
in Physical Review
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