Experimental measurement of collective nonlinear entanglement witness for two qubits

Karel Lemr, Karol Bartkiewicz, Antonín Černoch
2016 Physical Review A  
We present a proof-of-principle experiment demonstrating measurement of the collectibility, a nonlinear entanglement witness proposed by Rudnicki et al. [Phys. Rev. Lett. 107, 150502 (2011)]. This entanglement witness works for both mixed and pure two-qubit states. In the later case it can be used to measure entanglement in terms of the negativity. We measured the collectibility for three distinct classes of photonic polarization-encoded two-qubit states, i.e., maximally entangled, separable
more » ... maximally mixed states. We demonstrate that the measurement procedure is feasible and robust against typical experimental shortcomings such as imperfect two-photon indistinguishability.
doi:10.1103/physreva.94.052334 fatcat:mdat2czixvfhllbd2dv23dwxim