Entanglement and sudden death of two two-level atoms interacting with a cavity field in presence of degenerate parametric amplifier

In the presence of degenerate two-photon transitions the problem of the interaction between two two-level atoms and a single-mode is considered. Near resonance case, a closed form of the analytic solution for the wave function is obtained. The entanglement between an atom and field in the interacting system is studied by using the change in atomic and field entropies. The relationship between entropy changes and concurrence entanglement is discussed. Our results show that the behavior of the entropy change in agreement with the behavior of the concurrence to measure the entanglement between two subsystem structures.     

Quantum statistics of the degenerate parametric amplifier

From the quantum mechanics and the quantum optics point of view the problem of the time-dependent Hamiltonian which describes the degenerate parametric amplifier is presented. Under a certain integrability condition the solution of the Heisenberg equations of motion is given. The wave function for both the Schrödinger picture and quasi-coherent states, as well as the Green's function is obtained. The Glauber second order correlation function, and the squeezing and higher order squeezing is examined. The quasi-probability distribution function is also considered.     

Production of squeezed states in a degenerate parametric amplifier

An analysis of the degenerate parametric amplifier including the quantisation of pump and signal modes is presented. It is shown that the fluctuations in one quadrature of the signal mode may be reduced at most by a factor of two. This is in contradistinction to analyses where the pump field is treated classically which overestimate the reduction in fluctuations possible.     

简并参量下转换光场的统计性质

通过经(?)泵浦场的简并参量下转换过程的薛定谔方程的解,讨论了简并参量下转换光场的统计性质.     

A degenerate three-level laser with a parametric amplifier

The aim of this paper is to study the squeezing and statistical properties of the light produced by a degenerate three-level laser whose cavity contains a degenerate parametric amplifier. In this quantum optical system the top and bottom levels of the three-level atoms injected into the laser cavity are coupled by the pump mode emerging from the parametric amplifier. For a linear gain coefficient of 100 and for a cavity damping constant of 0.8, the maximum intracavity squeezing is found at steady state and at threshold to be 93%.     

Calculation of the photon-anticorrelation effect in a degenerate optical parametric amplifier

If two initially coherent light fields with the frequencies ω and 2ω, which have been produced by a second harmonic generator, pass a degenerate parametric amplifier photon-anticorrelation effects can develop. We calculate the time-development of the photon distribution for the signal wave by treating both fields quantum mechanically.     

Two-mode squeezing in a coherently driven degenerate parametric down conversion

Squeezing properties of a two-mode radiation produced by a process of driven degenerate parametric down conversion, when the cavity is coupled to two independent squeezed vacuum reservoirs employing the linearization procedure, are analyzed. The two-mode cavity and output radiations exhibit considerable squeezing even when the oscillator is coupled to a vacuum reservoir. One of the effects of coupling the cavity to the squeezed vacuum reservoirs is to increase the degree of squeezing exponentially. For the output radiation the correlation of the quadrature operators evaluated at different times also contributes to the squeezing, which is the reason for quenching of the overall noise in one of the quadrature components of the fundamental mode.     

Interaction of cavity solitons in degenerate optical parametric oscillators

Numerical studies, together with asymptotic and spectral analysis, establish regimes in which soliton pairs in degenerate optical parametric oscillators fuse, repel, or form bound states. A novel bound state that is stabilized by coupled internal oscillations is predicted.     

Electromagnetically induced transparency-like effect in the degenerate triple-resonant optical parametric amplifier

We investigate experimentally the absorptive and dispersive properties of the triple-resonant optical parametric amplifier (OPA) for the degenerate subharmonic field. In the experiment the subharmonic field is utilized as the probe field and the harmonic wave as the pump field. We demonstrate that the electromagnetically induced transparency (EIT)-like effect can be simulated in the triple-resonant OPA when the cavity linewidth for the harmonic wave is narrower than that for the subharmonic field. However, this phenomenon cannot be observed in a double-resonant OPA. The narrow transparency window appears in the reflected field. Especially in the measured dispersive spectra of the triple-resonant OPA, a very steep variation of the dispersive profile of the subharmonic field is observed, which can result in a slow light as that observed in an atomic EIT medium.     

Optomechanical properties of a degenerate nonperiodic cavity chain

Frontiers of Physics - Results of inelastic neutron scattering experiments and ab initio molecular dynamics simulations for GeTe–the parent compound of phase-change materials are reported....     

Evolution of cat states in a dissipative parametric amplifier: decoherence and entanglement

The evolution of the Schr?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). Received 25 September 2001 / Received in final form 30 May 2002 Published online 13 December 2002 RID="a" ID="a"e-mail: sebaweh@awalnet.net.sa RID="b" ID="b"Joint Laboratory of Optics of Palacky University and Institute of Physics, Academy of Sciences of the Czech Republic, 17. listopadu 50, 772 07 Olomouc, Czech Republic.     

Quantum images in non degenerate optical parametric oscillators

Quantum images, that is inhomogeneous field distributions purely generated by quantum fluctuations, persist when passing from the degenerate to the non-degenerate case of optical parametric oscillators (OPO). Below the threshold for parametric oscillation where the near-field distributions are homogeneous both in intensity and phase, appropriate spatial correlation functions anticipate the transverse spatial pattern that appears above threshold. In particular, the angular dependence of the far field spatial correlation function is able to reveal the travelling-wave nature of the phase pattern above threshold typical of nondegenerate OPOs. Cross-correlation functions between signal and idler intensities show clear evidence of the non-classical nature of the output light. Received 8 October 1999     

On the production of photon-anticorrelation effects in a degenerate parametric amplifier by means of partially coherent light fields

In order to obtain anticorrelated photons by means of nonlinear optical interactions, e.g., in an optical parametric amplifier, the incident light fields have to fulfill stringent criteria, which are calculated in the present paper. It is found that light fields with anticorrelated photons can only be obtained if the relative intensity fluctuations of the pump field are smaller than 2.5×10^–3.     

Pulse compression and gain enhancement in a degenerate optical parametric amplifier based on aperiodically poled crystals

We describe theoretically a method of obtaining pulse compression and simultaneously improving amplification in a degenerate optical parametric amplifier by use of quasi-phase-matched engineered crystals. The scheme combines the possibility of increasing the signal spectral bandwidth that is offered by a degenerate parametric amplifier with the ability of engineered aperiodically poled crystals to compensate for group-velocity mismatch.     

Statistical properties of the laser emission in a low-Q cavity

We investigate theoretically the stationary statistical properties of the laser radiation in a low-Q cavity with field, polarization, and population fluctuations. Eliminating adiabatically the electric field from the Maxwell-Bloch equations, coupled Langevin equations with bothadditive andmultiplicative noises are derived and are transformed into the multivariable Fokker-Planck equation of a probability density of the light intensity and the population difference. It is solved by the expansion into orthonormal sets, and a vector recurrence equation of motion of the expansion coefficients is given whose stationary solutions are analytically obtained in theMatrix continued-fraction. The stationary distribution function of the radiation intensity are calculated with several values of control parameters. We discuss the variance of the intensity distribution, the photon-counting coefficient, and the cross-correlation between intensity and population as a function of the pump parameter, and reveal the novel and characteristic features of the bad-cavity laser system. The comparison with the good-cavity (high-Q cavity) case is also made.     

Quantum statistical properties of the radiation field in the degenerate two-photon emission process

The degenerate two-photon emission process is treated on the basis of quantum theory. Neglecting relaxation mechanisms, solutions in short time approximation are given. Relevant quantities as the mean photon number, second order correlation, field fluctuations and the uncertainty product are analyzed. It is shown, that an initial coherent state does not tend to a two-photon coherent state by two-photon emission as it can be expected from the results given by Yuen.     

Statistical properties of the output of linear amplifier with superpositions of squeezed displaced Fock states as an input state

The s-parameterized characteristic function for the output field with the superposition of squeezed displaced Fock states (SDFS's) as input field is given. The s-ordered distribution functions for the output field with superposition of SDFS's as input state are investigated. Various moments are calculated by using the s-ordered characteristic function for that field. The Glauber second-order coherence function is calculated. The quadrature squeezing for the output field are discussed. Some Quasiprobability distribution functions of the output fields are plotted as functions of the interaction time. The quadrature squeezing for the output field are discussed. Received 30 September 1998