We present a scheme for broadcasting of continuous variable entanglement. We show how an initial two-mode squeezed state of the electromagnetic field shared by two distant parties can be broadcasted into two nonlocal bipartite entangled states. Our protocol uses a local linear amplifier and a beam splitter at each end. We compute the fidelity of the output entangled states and show that the broadcasting can be implemented for a variety of input squeezed states and amplifier phases.PACS numbers: 03.67. Mn,42.50.Dv Quantum entanglement is now recognized as a powerful resource in communication and computation protocols [1]. The first nontrivial consequence of entanglement on quantum ontology was noticed many years ago within the context of continuous variable systems [2]. In recent times there has been a rapid development of the theory of entanglement pertaining to infinite dimensional Hilbert spaces [3]. Many well-known results of discrete variable systems relating to classification and manipulation of entanglement take novel forms for the case of continuous variables [4]. There still remains a lot to be understood in the information theory for continuous variables which has potentially vast practical ramifications.An interesting issue is that of broadcasting of quantum entanglement, viz., whether the entanglement shared by a single pair can be transmitted to two less entangled pairs by local operations at both ends. Unlike classical correlations, quantum entanglement cannot always be broadcasted, as has been proved for general mixed states in finite dimensions [5]. Since broadcasting involves copying of local information, and the exact cloning of an unknown quantum state is impossible, the no-cloning theorem[6] and its consequences imply limitations on this procedure. For the case of pure states in finite dimensions, implementation of broadcasting imposes restrictions on the initial state[7] and conditions on the fidelity of the cloning process [8]. No scheme has yet been proposed, however, for the broadcasting of continuous variable entanglement.The cloning of continuous quantum variables has nonetheless, been studied by several authors. Various schemes for duplication of coherent states with optimal fidelity and economical means have been suggested [9]. Operations of cloning machines with networks of linear amplifiers and beam splitters have been proposed [10,11]. It is thus relevant to investigate whether such ideas of copying local information can be elaborated for broadcasting entangled states of continuous variables. To this end we extend the procedure of cloning of a single-mode squeezed state of the electromagnetic field proposed by Braunstein et al.[10] to the case of a bipartite entangled two-mode squeezed state. By applying a linear amplifier and a beam splitter available locally with each party, we show using the covariance matrix approach[4] how the initial entangled state can be broadcasted into two nonlocal and bipartite entangled states.Before describing our scheme for broadcasting in detail, i...
The RHIC high energy collision of species ranging from p+p, p(d)+A to A+A provide access to the small-x component of the hadron wave function. The RHIC program has brought renewed interest in that subject with its ability to reach values of the parton momentum fraction smaller than 0.01 with studies of particle production at high rapidity. Furthermore, the use of heavy nuclei in the p(d)+A collisions facilitates the study of saturation effects in the gluonic component of the nuclei because t8he appropriate scale for that regime grows as A i . We review the experimenta,l results of the RHIC program that have relevance to small-x emphasizing the physics extractled from d+Au collisions and their comparison to p+p collisions at the same energy.
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We investigate a Bell-type inequality for probabilities of detected atoms formulated using atom-photon interactions in a cavity. We consider decoherence brought about by both atomic decay, as well as cavity photon loss, and study its quantitative action in diminishing the atom-field and the resultant atom-atom secondary correlations. We show that the effects of decoherence on nonlocality can be observed in a controlled manner in actual experiments involving the micromaser and also the microlaser.Comment: 9 pages, 3 .eps figures, Revtex. Revised version with details of calculations and more result
We consider various dissipative atom-cavity systems and show that their collective dynamics can be used to maximize entanglement for intermediate values of the cavity leakage parameter κ. We first consider the interaction of a single two-level atom with one of two coupled microwave cavities and show analytically that the atom-cavity entanglement increases with cavity leakage. We next consider a system of two atoms passing successively through a cavity and derive the expression for the maximum value of κ in terms of the Rabi angle gt, for which the two-atom entanglement can be increased. Finally, numerical investigation of micromaser dynamics also reveals the increase of two-atom entanglement with stronger cavity-environment coupling for experimentally attainable values of the micromaser parameters.
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