Schrodinger Cat States Research Articles

Relaxation of Schrödinger Cat States and Displaced Thermal States in a Density Operator Representation

Damping of quantum superposition of displaced states such as a Schrodinger cat state and a displaced thermal state interacting with a thermal reservoir is studied in a density operator formalism. The master equation approach is employed and the solution is shown to be factorized to a thermal density operator and displacement operators. This formalism is applied to the cat generating experiment proposed by Brune et al. [Phys. Rev. A 45 (1992) 5193], and the field evolution is obtained analytically.

The quantum sling and the Schrödinger cat

The quantum sling is defined as a quantum harmonic oscillator with an abruptly vanishing frequency. It is shown in this article that a particle released by such a mechanism remains in acorrelated coherent state, i.e., a quantum state with the minimum dispersion in position and momentum allowed by the Schrodinger-Robertson uncertainty principle. This simple model permits to describe a Schrodinger-cat state (a quantum superposition of macroscopically distinguishable states) released by the sling. The result is a superposition of two correlated coherent states propagating in two opposite directions and with an interference term.

Entropic uncertainty relations for a quantum oscillator

We calculated the Shannon entropy of position and momentum for the stationary quantum states of the harmonic oscillator as a function of its energy and determined the corresponding entropic uncertainty relations for them. We found an approximate phenomenological function for the dependence of position and momentum entropies on the large quantum numbers and the corresponding asymptotic entropy - energy relation for the stationary harmonic oscillator. We also studied the time evolution of the position and momentum entropies of the non-stationary harmonic oscillator for the coherent states, squeezed vacuum and Schrodinger cat states.

Dipole states in the deuteron, other exotic nuclei, and “Schrödinger’s Cat”

The question whether the “soft giant dipole modes” in alo nuclei are resonances is discussed. It is argued that a resonance picture of these modes can be envisaged with a non Breit-Wigner line shape. The dipole Coulomb breakup of the deuteron is worked out as a specific example of such a picture. The “soft” and “hard” dipole modes of the more complex neutron-rich exotic nuclei are treated from this point of view. An interpretation of the coherent production of these modes in Coulomb excitation as a nuclear instance of Schrodinger cat state is advanced.

PRODUCTION AND DETECTION OF SCHRDINGER CAT STATE AND ITS EFFECT ON THE EVOLUTION OF JAYNES-CUMMINGS MODEL

In this article, we have studied how to generate macroscopic quantum superposition states in electromagnetic field, the Schrodinger cat states, from the large-detuning degenerate Raman process and the large-detuning two-photon Jaynes-Cummings model. The homodyne detection of these states is also discussed. When the initial state of the field is the Schrodinger cat state, the effects of the cat state on the collapse and revival phenomena in the intensity-dependent Jaynes-Cummings model are investigated. The revival in varying degrees occurs in the collapse region resulted from the evolution of initial coherent state.

Crystallized schrödinger cat states

Crystallized Schrodinger cat states (male and female) are introduced on the base of extension of group construction for the even and odd coherent states of the electromagnetic field oscillator. The Wigner and Q functions are calculated and some are plotted forC2,C3,C4,C5,C3v Schrodinger cat states. Quadrature means and dispersions for these states are calculated and squeezing and correlation phenomena are studied. Photon distribution functions for these states are given explicitly and are plotted for several examples. A strong oscillatory behavior of the photon distribution function for some field amplitudes is found in the new type of states.

Geometric phases and Schrödinger's cat state

A matrix method is presented for treating the dynamical phases, adiabatic phases and nonadiabatic phases of quantum superposition states. It is effective for any parameter-varying Hamiltonian system. As two examples, the evolution of mass-varying harmonic oscillator and the evolution of coherent states under parameter-varying displaced operator have been studied, Some new phenomena are obtained in the first case and the possible producing of so-called Schrodinger's cat state by geometric phases is pointed out. The quantum state useful for the quantum optical verification of Berry's phase is introduced.

Optical Schrodinger-cat states in a directional coupler

The evolution of an optical Schrodinger-cat state in a linear coupler is presented. It is shown how the quantum interference of the cat state deteriorates and recovers along the channels of the device. A similar behaviour of the photon number distribution pattern is noted.

Squeezing in multimode Schrödinger cat states

Multimode generalization of Schrodinger cat states of light is discussed. Two-mode Schrodinger cat states are considered as an example. Squeezing in even and odd coherent states of a two-mode field is studied.

Interaction of Schrödinger cats in optical processes

The propagation of optical Schrödinger cat states is considered in beam-splitters and parametric amplifiers. Special attention is paid to the evolution of the fringe pattern in the Wigner function picture characteristic of the quantum interference in Schrödinger cat states. The connection between the variation of quantum features, especially the squeezing, and the evolution of the fringe pattern in these optical processes is revealed. The behaviour of the even coherent state in the amplification process is compared with that of the squeezed coherent states.

Cooperativity and Entanglement of Atom-field States

Abstract The Jaynes-Cummings model of a single two-level atom interacting with a quantized single-mode coherent field generates at the half-revival time a dynamically disentangled atom-field state. At such times, the field is in asymptotically pure Schrodinger cat state, a macroscopic superposition of distinct field eigenmodes. In this paper we address the problem of field purity when a second atom is allowed to interact with the cavity mode and becomes entangled with the first atom via their mutual cavity field with which they interact. We employ the collective Dicke states to describe the cooperative effects on the entanglement and show that the second atom spoils the purity of the field state except for special cases of the atom-field coupling or of initial conditions.

Macroscopic Superposition States of Light Via Two-photon Resonant Interaction of Atoms with Cavity Field

Abstract We show that the resonant interaction between a two-level atom and a quantized field mode via two-photon transitions leads to extreme quantum entanglement between the atom and quantum field. Nevertheless during the time evolution there are moments at which the atom-field system becomes asymptotically disentangled. We investigate statistical properties of the pure-field states generated at such times. We show that at the quarter of the revival time the field is produced in the pure superposition state (Schrodinger cat state) composed of two coherent states with the same amplitude but which are out of phase by 90° (we obtain approximate analytical solution for this superposition state). We show that the interference between component states leads to non-classical oscillations in the photon number distribution. At the revival time the field is again in the pure state (we present an approximate analytical solution for the corresponding state vector). This pure state is not a superposition state. Neve...

Amplification of superposition states in phase-sensitive amplifiers.

We study statistical properties of quantum superposition states (Schrodinger-cat states) amplified by phase-sensitive (squeezed) amplifiers. We show that the phase-sensitive amplifier with a properly chosen phase can preserve quantum coherences and nonclassical behavior of the Schrodinger-cat-state input even for a gain factor G larger than 2. In particular, we show that for an even coherent state (CS) phase-sensitive amplifiers can preserve squeezing for G>2 but simultaneously in the process of amplification the noise added by the amplifier leads to a rapid increase of fluctuations in the photon number. Because of the finite maximum degree of squeezing obtainable for the even CS the maximum gain factor G m for which squeezing can still be observed in the output state is finite

Decay of Quantum Coherences Under the Influence of a Thermal Heatbath

Recently several methods have been proposed for generation of superposition (Schrodinger cat) states in microwave cavities. At microwave frequencies thermal photons can significantly affect statistical properties of superposition states. In the present letter we study the influence of a thermal heatbath on non-classical properties of quantum superposition states. We show that at non-zero temperatures the loss of quantum coherences is much faster than at zero temperature and that the sensitivity of the quantum coherence to the presence of thermal photons can lead to some difficulties in the preparation of Schrodinger cat states in microwave cavities unless the temperature of the microwave cavity is sufficiently low.