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Physical Review A

Separation of quantum correlated particles by a heat bath

Nicolas Gisin

Published Nov 1, 1983• 2 citations
Publisher

Abstract

We consider the action of a heat bath on one particle of a pair of spin-$\frac{1}{2}$ particles in a singlet state. The related relaxation effects are described by the Pauli master equation. We show that the density matrix of the two-particle system tends toward a product. The interpretation of this result is, however, complicated by the nonuniqueness of the decomposition of a given density matrix into pure states. To circumvent this difficulty we study separately the terms describing the fluctuations and the friction. The first one does not modify the correlations, although it screens them but the second one separates the systems. The action of a fluctuating magnetic field on one particle of a correlated pair is also investigated.

DOI
10.1103/physreva.28.2981

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The dynamics of a maximally entangled pair of spin-1/2 particles is obtained in the presence of random magnetic fields which are correlated. The two spin-1/2 particles are assumed to be maximally entangled initially and are then disturbed by the magnetic fields modeled as Gaussian vector random processes whose corresponding spatial components are correlated. The dynamics is derived in terms of the joint density matrix of the entangled pair using the ideas of stochastic calculus, from which the steady-state density matrix and the associated timescale for it to be reached are obtained. The asymptotic density matrix represents a state of (partial) disentanglement.