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    P systems with communication based on concentration

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    We consider a variant of P systems where the communication of objects is controlled by the "concentration" of these objects: after each evolution step, the objects are redistributed among the regions of the system in such a way that each region contains the same number of copies of each object (plus/minus one, when the number of objects is not divisible by the number of regions). We show that P systems of this form, with only one flip-flop catalyst but without using other control ingredients, can generate the Parikh images of all matrix languages. When an unbounded number of catalysts is available, a characterization of recursively enumerable sets of vectors of natural numbers is obtained (by systems with only one membrane)

    Single-photon-assisted entanglement concentration of a multi-photon system in a partially entangled W state with weak cross-Kerr nonlinearity

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    We propose a nonlocal entanglement concentration protocol (ECP) for NN-photon systems in a partially entangled W state, resorting to some ancillary single photons and the parity-check measurement based on cross-Kerr nonlinearity. One party in quantum communication first performs a parity-check measurement on her photon in an NN-photon system and an ancillary photon, and then she picks up the even-parity instance for obtaining the standard W state. When she obtains an odd-parity instance, the system is in a less-entanglement state and it is the resource in the next round of entanglement concentration. By iterating the entanglement concentration process several times, the present ECP has the total success probability approaching to the limit in theory. The present ECP has the advantage of a high success probability. Moreover, the present ECP requires only the NN-photon system itself and some ancillary single photons, not two copies of the systems, which decreases the difficulty of its implementation largely in experiment. It maybe have good applications in quantum communication in future.Comment: 7 pages, 3 figure

    Optimal nonlocal multipartite entanglement concentration based on projection measurements

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    We propose an optimal nonlocal entanglement concentration protocol (ECP) for multi-photon systems in a partially entangled pure state, resorting to the projection measurement on an additional photon. One party in quantum communication first performs a parity-check measurement on her photon in an N-photon system and an additional photon, and then she projects the additional photon into an orthogonal Hilbert space for dividing the original NN-photon systems into two groups. In the first group, the N parties will obtain a subset of NN-photon systems in a maximally entangled state. In the second group, they will obtain some less-entangled N-photon systems which are the resource for the entanglement concentration in the next round. By iterating the entanglement concentration process several times, the present ECP has the maximal success probability which is just equivalent to the entanglement of the partially entangled state. That is, this ECP is an optimal one.Comment: 5 pages, 4 figure
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