There are tasks for which Bound entangled states (BEs) are not useful, however they can help to perform these tasks in conjunction with other states. For example every bipartite bound entangled state can increase optimal fidelity of teleportation via some state $\backslash rho$ even though the BEs itself offers teleportation fidelity which can be achieved with only classical resources. Such phenomenon is called activation of bound entanglement.
There are multipartite bound entangled states such that put together constitute a state that is no longer bound entangled. I.e. $\backslash rho\_1\; \backslash otimes\; \backslash rho\_2$ is not bound entangled even though both $\backslash rho\_1$ and $\backslash rho\_2$ are bound entangled. Such phenomenon is called superactivation. For bipartite state superactivation is possible if there exists an NPT BEs
Category:Quantum Information Theory

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Monday, October 26, 2015 - 17:56