Phase space interference and the WKB approximation for squeezed number states

Squeezed number states for a single mode Hamiltonian are investigated from two complementary points of view. Firstly the more relevant features of their photon distribution are discussed using the WKB wave functions. In particular the oscillations of the distribution and the parity behavior are derived and compared with the exact results. The accuracy is verified and it is shown that for high photon number it fails to reproduce the true distribution. This is contrasted with the fact that for moderate squeezing the WKB approximation gives the analytical justification to the interpretation of the oscillations as the result of the interference of areas with definite phases in phase space. It is shown with a computation at high squeezing using a modified prescription for the phase space representation which is based on Wigner-Cohen distributions that the failure of the WKB approximation does not invalidate the area overlap picture.Comment: 9 pages, 4 figure

Creation of photons in an oscillating cavity with two moving mirrors

We study the creation of photons in a one dimensional oscillating cavity with two perfectly conducting moving walls. By means of a conformal transformation we derive a set of generalized Moore's equations whose solution contains the whole information of the radiation field within the cavity. For the case of resonant oscillations we solve these equations using a renormalization group procedure that appropriately deals with the secular behaviour present in a naive perturbative approach. We study the time evolution of the energy density profile and of the number of created photons inside the cavity.Comment: LaTex file, 17 pages, 3 figures, uses epsf.st

Quantum electromagnetic field in a three dimensional oscillating cavity

We compute the photon creation inside a perfectly conducting, three dimensional oscillating cavity, taking the polarization of the electromagnetic field into account. As the boundary conditions for this field are both of Dirichlet and (generalized) Neumann type, we analyze as a preliminary step the dynamical Casimir effect for a scalar field satisfying generalized Neumann boundary conditions. We show that particle production is enhanced with respect to the case of Dirichlet boundary conditions. Then we consider the transverse electric and transverse magnetic polarizations of the electromagnetic field. For resonant frequencies, the total number of photons grows exponentially in time for both polarizations, the rate being greater for transverse magnetic modes.Comment: 11 pages, 1 figur

Motion-Induced Radiation from a Dynamically Deforming Mirror

A path integral formulation is developed to study the spectrum of radiation from a perfectly reflecting (conducting) surface. It allows us to study arbitrary deformations in space and time. The spectrum is calculated to second order in the height function. For a harmonic traveling wave on the surface, we find many different regimes in which the radiation is restricted to certain directions. It is shown that high frequency photons are emitted in a beam with relatively low angular dispersion whose direction can be controlled by the mechanical deformations of the plate.Comment: 4 pages, 2 eps figues included, final version as appeared in PR

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

Quantum radiation pressure on a moving mirror at finite temperature

We compute the radiation pressure force on a moving mirror, in the nonrelativistic approximation, assuming the field to be at temperature $T.$ At high temperature, the force has a dissipative component proportional to the mirror velocity, which results from Doppler shift of the reflected thermal photons. In the case of a scalar field, the force has also a dispersive component associated to a mass correction. In the electromagnetic case, the separate contributions to the mass correction from the two polarizations cancel. We also derive explicit results in the low temperature regime, and present numerical results for the general case. As an application, we compute the dissipation and decoherence rates for a mirror in a harmonic potential well.Comment: Figure 3 replaced, changes mainly in Sections IV and V, new appendix introduced. To appear in Physical Review

Fluctuations, dissipation and the dynamical Casimir effect

Vacuum fluctuations provide a fundamental source of dissipation for systems coupled to quantum fields by radiation pressure. In the dynamical Casimir effect, accelerating neutral bodies in free space give rise to the emission of real photons while experiencing a damping force which plays the role of a radiation reaction force. Analog models where non-stationary conditions for the electromagnetic field simulate the presence of moving plates are currently under experimental investigation. A dissipative force might also appear in the case of uniform relative motion between two bodies, thus leading to a new kind of friction mechanism without mechanical contact. In this paper, we review recent advances on the dynamical Casimir and non-contact friction effects, highlighting their common physical origin.Comment: 39 pages, 4 figures. Review paper to appear in Lecture Notes in Physics, Volume on Casimir Physics, edited by Diego Dalvit, Peter Milonni, David Roberts, and Felipe da Rosa. Minor changes, a reference adde

Derivation of the statistics of quantum measurements from the action of unitary dynamics

[[abstract]]Quantum statistics is defined by Hilbert space products between the eigenstates associated with state preparation and measurement. The same Hilbert space products also describe the dynamics generated by a Hamiltonian when one of the states is an eigenstate of energy E and the other represents an observable B . In this paper, we investigate this relation between the observable time evolution of quantum systems and the coherence of Hilbert space products in detail. It is shown that the times of arrival for a specific value of B observed with states that have finite energy uncertainties can be used to derive the Hilbert space product between eigenstates of energy E and eigenstates of the dynamical variable B . Quantum phases and interference effects appear in the form of an action that relates energy to time in the experimentally observable dynamics of localized states. We illustrate the relation between quantum coherence and dynamics by applying our analysis to several examples from quantum optics, demonstrating the possibility of explaining non-classical statistics in terms of the energy-time relations that characterize the corresponding transformation dynamics of quantum systems.[[notice]]補正完