Four-party unlockable bound entangled state - art. no. 032306

I present a four-party unlockable bound entangled state, that is, a four-pa rty quantum state which cannot be written in a separable form and from whic h no pure entanglement can be distilled by local quantum operations and cla ssical communication among the parties, and yet when any two of the parties come together in the same laboratory they can perform a measurement which enables the other two parties to create a pure maximally entangled state be tween them without coming together. This unlocking ability can be viewed in two ways, either as a determination of which Bell state is shared in the m ixture or as a kind of quantum teleportation with cancellation of Pauli ope rators.