Local observables for entanglement witnesses

G. Mauro D'Ariano, Chiara Macchiavello, Matteo G. A. Paris

Published 2002-11-22, updated 2003-01-21Version 2

We present an explicit construction of entanglement witnesses for depolarized states in arbitrary finite dimension. For infinite dimension we generalize the construction to twin-beams perturbed by Gaussian noises in the phase and in the amplitude of the field. We show that entanglement detection for all these families of states requires only three local measurements. The explicit form of the corresponding set of local observables (quorom) needed for entanglement witness is derived.