title: Mach-Zehnder interferometry at the Heisenberg limit with coherent and squeezed-vacuum light.
abstract: We show that the phase sensitivity Deltatheta of a Mach-Zehnder interferometer illuminated by a coherent state in one input port and a squeezed-vacuum state in the other port is (i) independent of the true value of the phase shift and (ii) can reach the Heisenberg limit Deltatheta approximately 1/N(T), where N(T) is the average number of input particles. We also demonstrate that the Cramer-Rao lower bound of phase sensitivity, Deltatheta approximately 1/square root[|alpha|(2)e(2r)+sinh(2)r], can be saturated for arbitrary values of the squeezing parameter r and the amplitude of the coherent mode alpha by using a Bayesian phase inference protocol.
authors: BEC-CNR-INFM and Dipartimento di Fisica, Università di Trento, I-38050 Povo, Italy.
authors: Luca
authors: L
authors: Pezzé
authors: Augusto
authors: A
authors: Smerzi