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Journal of Physics B Atomic Molecular and Optical Physics

Decoherence of entangled states in two-mode cavities

Maciej Janowicz, Arkadiusz Orłowski

Published Mar 21, 2006• 8 citations
Publisher

Abstract

Decoherence of the Schrodinger-cat states in two-mode cavities are discussed. The cat states are assumed to be produced by the measurement of the energy of a three-level atom which have passed through the cavity. The evolution of the field density matrix is obtained from the Lindblad form of the dissipater at zero temperature. It is shown that the decoherence time of the two-mode cat states critically depends on the degree of entanglement. Implications for decoherence of entanglement in the macroscopic scales are discussed.

DOI
10.1088/0953-4075/39/7/018

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Decoherence of the Schrodinger-cat states in two-mode cavities are discussed. The cat states are assumed to be produced by the measurement of the energy of a three-level atom which have passed through the cavity. The evolution of the field density matrix is obtained from the Lindblad form of the dissipater at zero temperature. It is shown that the decoherence time of the two-mode cat states critically depends on the degree of entanglement. Implications for decoherence of entanglement in the macroscopic scales are discussed.
In this paper, we investigate the temporal evolution of various measures of degree of entanglement and total correlation of a single-mode light field interacting with a two-level atom. The phase-damped cavity is taken into account. The effects of phase damping on a temporal of partial entropies for the atom and the field, total entropy, the entropy difference and the sum of negative eigenvalues of the partially transposed density matrix as a quantitative entanglement measure for the master equation in the dressed-state approximation are taken into account.
In this paper we investigated the entanglement dynamics of a pair of two-level atoms passing through a vacuum or thermal cavity one after another. We assumed that two atoms were initially prepared in separable coherent or entangled states. Using the exact solution of the density matrix evolution equation we calculated the time dependence of negativity for models with one-and two-photon interaction between atoms and the cavity field. For the two-photon model we took into account the dynamical Stark shift. We have found that the degree of atom-atom entanglement can be controlled by the Stark shift and cavity mean photon numbers.
The dynamics of quantum decoherence have been experimentally studied for the first time. A single circular Rydberg atom prepares in a high-quality superconducting cavity a ‚Schrödinger cat‘ state of the radiation field. This highly non-classical state is a quantum superposition of two coherent components with different classical phases. A second atom probes the cavity state after a tunable delay. The decay of the quantum correlations between the two atoms reveals the evolution of the initial quantum superposition into a mere statistical mixture. The time scale of this process decreases when the separation beween the two components increases. A simple theoretical model of the experiment is presented. The excellent agreement with the experimental signals confirms in a striking way the decoherence approach.
By the negative eigenvalues of partial transposition of density matrix, this paper investigates the time evolution of entanglement of the two entangled atoms in the system of two atoms interacting with Schrödinger cat state. The result shows that the two atoms are always in the entanglement state, and the degree of entanglement between the two atoms exhibits ordinary collapses and revivals at 0.2 degree of entanglement, when the light field is large enough. On the other hand, the reinforcement of three different light fields on the degree of entanglement between two atoms is not evident.
We provide a scheme by utilizing a two-cavity setup to generate useful quantum mechanically entangled states of two cavity fields, which themselves are prepared in Schrodinger cat states. The underlying atom-field interaction is considered off-resonant and three atoms are successively sent through the cavities, initially fed with coherent fields. Analytical solution of the protocol, followed by conditional measurements on the atoms, produce a family of eight such entangled states. Entanglement properties of the obtained states are characterized by the Von Neumann entropy. We reveal the parameter domain for tuning the entanglement, the prime tuning parameters being the atom-field interaction time and the field amplitudes. The parameter domains for both quasi-Bell and non quasi-Bell states are discussed. We also present a Wigner phase space representation of the reduced state of the cavity, showing negative values and interference patterns similar to those of a compass state, used in quantum precision measurements, and despite its large entropy.
A single circular Rydberg atom is used to prepare in a high quality superconducting cavity a “Schrödinger cat” state, quantum superposition of two coherent fields with different classical phases. A second atom probes the cavity state after a tunable delay. The decay of the quantum correlations between the two atoms reveals the evolution of the field state from an initial quantum superposition into a mere statistical mixture. The time scale of this decay decreases when the separation between the two components increases. This is the first experimental observation of the dynamics of decoherence, lying at the heart of the quantum measurement process.