Single observable concurrence measurement without simultaneous copies
A. Salles, Fernando de Melo, J. C. Retamal, R. L. de Matos Filho, Nicim Zagury · Physical Review A · 2006
We present a protocol that allows us to obtain the concurrence of any two-qubit pure state by performing a minimal and optimal tomography of one of the subsystems through measuring a single observable of an ancillary four-dimensional qudit. An implementation for a system of trapped ions is also proposed, which can be achieved with present-day experimental techniques.