Construction of an Optimal Witness for Unknown Two-Qubit Entanglement
Construction of an Optimal Witness for Unknown Two-Qubit Entanglement
Whether entanglement in a state can be detected, distilled, and quantified without full state reconstruction is a fundamental open problem. We demonstrate a new scheme encompassing these three tasks for arbitrary two-qubit entanglement, by constructing the optimal entanglement witness for polarization-entangled mixed-state photon pairs without full state reconstruction. With better …