Input States for Enhancement of Fermion Interferometer Sensitivity

A conventional fermion interferometer, in which the fermions enter only one of the two input ports, can achieve a phase sensitivity =1n, where n is the total number of fermions which have passed through the interferometer. Here it is shown that by injection of fermions into both input ports the phase sensitivity can approach 1n provided that the fermions in the two input beams are suitably correlated.