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arXiv:1805.11337 · Physical Review A

Experimental measurement of a nonlinear entanglement witness by hyperentangling two-qubit states

Vojtěch Trávníček, Karol Bartkiewicz, Antonín Černoch, Karel Lemr

Published Sep 7, 2018• 11 citations
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Abstract

We demonstrate that nonlinear entanglement witnesses can be made particularly useful for entanglement detection in hyperentangled or multilevel states. We test this idea experimentally on the platform of linear optics using a hyperentangled state of two photons. Instead of several simultaneous copies of two-photon entangled states, one can directly measure the witness on a single copy of a hyperentangled state. Our results indicate that hyperentanglement can be used for quick entanglement detection and it provides a practical test bed for experiments with nonlinear entanglement witnesses.

DOI
10.1103/physreva.98.032307

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We present a nonlinear entanglement detection strategy that detects entanglement that the linear detection strategy fails. We show that when the nonlinear entanglement detection strategy fails to detect the entanglement of an entangled state with two copies, it may succeed with three or more copies. Based on our strategy, a witness combined with a suitable quantum mechanical observable may detect the entanglement that cannot be detected by the witness alone. Moreover, our strategy can also be applied to detect multipartite entanglement by using the witnesses for bipartite systems, as well as to entanglement concentrations.
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