Experimental measurement of a nonlinear entanglement witness by hyperentangling two-qubit states
Vojtěch Trávníček, Karol Bartkiewicz, Antonín Černoch, Karel Lemr · Physical Review A · 2018
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.