Experimental Bound Entanglement in a Four-Photon State
Jonathan Lavoie, Rainer Kaltenbaek, Marco Piani, Kevin J. Resch · Physical Review Letters · 2010
Bound entanglement is central to many exciting theoretical results in quantum information processing, but has thus far not been experimentally realized. In this work, we consider a one-parameter family of four-qubit Smolin states. We experimentally produce these states in the polarization of four optical photons produced from parametric down-conversion. Within a range of the parameter, we show that our states are entangled and undistillable, and thus bound entangled. Using these bound-entangled states we demonstrate entanglement unlocking.