Reply to 'Experimental bound entanglement?'

Jonathan Lavoie, Rainer Kaltenbaek, Marco Piani +1 more

Jonathan Lavoie, Rainer Kaltenbaek, Marco Piani +1 more

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.

Henry M. van Driel

Gael Sentís, Johannes N. Greiner, Jiangwei Shang +2 more

Preparing and certifying bound entangled states in the laboratory is an intrinsically hard task, due to both the fact that they typically form narrow regions in state space, and that a certificate requires a tomographic reconstruction of the density matrix. Indeed, the previous experiments that have reported the preparation of a bound entangled state relied on such tomographic reconstruction techniques. However, the reliability of these results crucially depends on the extra assumption of an unbiased reconstruction. We propose an alternative method for certifying the bound entangled character of a quantum state that leads to a rigorous claim within a desired statistical significance, while bypassing a full reconstruction of the state. The method is comprised by a search for bound entangled states that are robust for experimental verification, and a hypothesis test tailored for the detection of bound entanglement that is naturally equipped with a measure of statistical significance. We apply our method to families of states of 3×3 and 4×4 systems, and find that the experimental certification of bound entangled states is well within reach.

Francesco Riggi

Fumihiro Kaneda, Ryōsuke Shimizu, Satoshi Ishizaka +3 more

We report the experimental realization of the four-partite bound-entangled state, i.e., Smolin state and demonstrate the 'superactivation' of the bound entanglement. Bound entanglement is a class of multipartite entanglement that cannot be distilled into pure entanglement under local operations and classical communication (LOCC).