arXiv subjects

S. G. Mokarzel

Publications and source records attributed to S. G. Mokarzel.

4 recordsLinked to original sources

arXiv2004

Decay rate and decoherence control in coupled dissipative cavities

We give a detailed account of the derivation of a master equation for two coupled cavities in the presence of dissipation. The analytical solution is presented and physical limits of interest are discussed. Firstly we show that the decay rate of initial coherent states can be significantly modified if the two cavities have different decay rates and are weakly coupled through a wire. Moreover, we show that also decoherence rates can be substantially altered by manipulation of physical parameters. Conditions for experimental realizations are discussed.

quant-ph↗

arXiv2003

Realistic Decoherence Free Subspaces

Decoherence free subspaces (DFS) is a theoretical tool towards experimental implementation of quantum information storage and processing. However, they represent an experimental challenge, since conditions for their existence are very stringent. This work explores the situation in which a system of $N$ oscillators coupled to a bath of harmonic oscillators is close to satisfy the conditions for the existence of DFS. We show, in the Born-Markov limit and for small deviations from separability and degeneracy conditions, that there are {\emph{weak decoherence subspaces}} which resemble the original notion of DFS.

quant-ph↗

arXiv2002

Decoherence Sturdy Memories in the Presence of Quantum Dissipation

We consider N identical oscillators coupled to a single environment and show that the conditions for the existence of decoherence free subspaces are degeneracy of the oscillator frequencies and separability of the coupling with the environment. A formal exact equation for the evolution in the case of two oscillators is found and the decoherence free subspace is explicitly determined. A full analytical solution for any initial condition and general parameters (frequencies and dissipation constants) is given in the markovian approximation and zero temperature. We find that slight relaxation of degeneracy and separability conditions leads to the appearence of two components in the dynamical evolution with very different decoherence times. The ratio between the characteristic time of the weak and strong decoherent components is given by $τ_{WD}/τ_{SD}\approx k/δk$, where $δk$ is a measure of the nonseparability of the coupling to the environment and $k$ is the mean decay constant of the oscillators.

quant-ph↗

arXiv2001

Modelling the Recoherence of Mesoscopic Superpositions in Dissipative Environments

A model is presented to describe the recently proposed experiment (J. Raimond, M. Brune and S. Haroche Phys. Rev. Lett {\bf 79}, 1964 (1997)) where a mesoscopic superposition of radiation states is prepared in a high-Q cavity which is coupled to a similar resonator. The dynamical coherence loss of such state in the absence of dissipation is reversible and can in principle be observed. We show how this picture is modified due to the presence of the environmental couplings. Analytical expressions for the experimental conditional probabilities and the linear entropy are given. We conclude that the phenomenon can still be observed provided the ratio between the damping constant and the inter-cavities coupling does not exceed about a few percent. This observation is favored for superpositions of states with large overlap.

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