707 research outputs found
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
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
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
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
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
Quantum radiation reaction force on a one-dimensional cavity with two relativistic moving mirrors
We consider a real massless scalar field inside a cavity with two moving
mirrors in a two-dimensional spacetime, satisfying Dirichlet boundary condition
at the instantaneous position of the boundaries, for arbitrary and relativistic
laws of motion. Considering vacuum as the initial field state, we obtain
formulas for the exact value of the energy density of the field and the quantum
force acting on the boundaries, which extend results found in previous papers.
For the particular cases of a cavity with just one moving boundary,
non-relativistic velocities, or in the limit of infinity length of the cavity
(a single mirror), our results coincide with those found in the literature.Comment: 6 pages 9 figure
Purity and Gaussianity bounded uncertainty relation
Bounded uncertainty relations provide the minimum value of the uncertainty
assuming some additional information on the state. We derive analytically an
uncertainty relation bounded by a pair of constraints, those of purity and
Gaussianity. In a limiting case this uncertainty relation reproduces the
purity-bounded derived by V I Man'ko and V V Dodonov and the
Gaussianity-bounded one [Phys. Rev. A 86, 030102R (2012)].Comment: Major changes in the presentation of the results but also in the
proofs which have become more compact. Submitted to Journal of Physics
Dynamical Casimir Effect in a Leaky Cavity at Finite Temperature
The phenomenon of particle creation within an almost resonantly vibrating
cavity with losses is investigated for the example of a massless scalar field
at finite temperature. A leaky cavity is designed via the insertion of a
dispersive mirror into a larger ideal cavity (the reservoir). In the case of
parametric resonance the rotating wave approximation allows for the
construction of an effective Hamiltonian. The number of produced particles is
then calculated using response theory as well as a non-perturbative approach.
In addition we study the associated master equation and briefly discuss the
effects of detuning. The exponential growth of the particle numbers and the
strong enhancement at finite temperatures found earlier for ideal cavities turn
out to be essentially preserved. The relevance of the results for experimental
tests of quantum radiation via the dynamical Casimir effect is addressed.
Furthermore the generalization to the electromagnetic field is outlined.Comment: 48 pages, 8 figures typos corrected & references added and update
Measuring microwave quantum states: tomogram and moments
Two measurable characteristics of microwave one-mode photon states are
discussed: a rotated quadrature distribution (tomogram) and
normally/antinormally ordered moments of photon creation and annihilation
operators. Extraction of these characteristics from amplified microwave signal
is presented. Relations between the tomogram and the moments are found and can
be used as a cross check of experiments. Formalism of the ordered moments is
developed. The state purity and generalized uncertainty relations are
considered in terms of moments. Unitary and non-unitary time evolution of
moments is obtained in the form of linear differential equations in contrast to
partial differential equations for quasidistributions. Time evolution is
specified for the cases of a harmonic oscillator and a damped harmonic
oscillator, which describe noiseless and decoherence processes, respectively.Comment: 10 pages, 1 figure, to appear in Phys. Rev.
An Optical Approach to the Dynamical Casimir Effect
We recently proposed a new approach to analyze the parametric resonance in a
vibrating cavity based on the analysis of classical optical paths. This
approach is used to examine various models of cavities with moving walls. We
prove that our method is useful to extract easily basic physical outcome.Comment: 9 page
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