Biomedical subjects
Publications and source records attributed to P Horodecki.
We investigate multiparty communication scenarios where information is sent from several senders to several receivers. We establish a relation between the quantum capacity of multiparty communication channels and their distillability properties, which enables us to show that the quantum capacity of such channels is not additive.
We introduce the definition of generic bound entanglement for the case of continuous variables. We provide some examples of bound entangled states for that case, and discuss their physical sense in the context of quantum optics. We raise the question of whether the entanglement of these states is generic. As a by-product we obtain a new many parameter family of bound entangled states with positive partial transpose. We also point out that the "entanglement witnesses" and positive maps revealing the corresponding bound entanglement can easily be constructed.
Based on a unified approach to all kinds of quantum capacities we show that the rate of quantum information transmission is bounded by the maximal attainable rate of coherent information. Moreover, we show that if for any bipartite state the one-way distillable entanglement is no less than coherent information, then one obtains Shannon-like formulas for all the capacities. The inequality also implies that the decrease of distillable entanglement due to the mixing process does not exceed that of the corresponding loss of information about a system.
It is commonly believed that distillation of entanglement can be, in general, irreversible. Perhaps the strongest evidence is constituted by the existence of the bound entangled states. However, even a single example of state exhibiting this irreversibility has not been found so far. We show that for a family of states the process of distillation of entanglement is truly irreversible. These states have a nonzero amount of bound entanglement and, at most, a very small amount of free entanglement.
The basic principle of entanglement processing says that entanglement cannot increase under local operations and classical communication. Based on this principle, we show that any entanglement measure E suitable for the regime of a high number of identically prepared entangled pairs satisfies ED < or = E < or = EF, where ED and EF are the entanglement of distillation and formation, respectively. Moreover, we exhibit a theorem establishing a very general form of bounds for distillable entanglement.
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