THE PHASE-SENSITIVITY OF A MACH-ZEHNDER INTERFEROMETER FOR THE FOCK STATE INPUTS

Phase-sensitivity of some different measurement schemes with a Mach-Ze hnder interferometer is studied. The input light is considered to be i n a photon number state and the detectors are assumed to be ideal with quantum efficiency of unity. Direct calculation of the operators corr esponding to the measurement schemes shows that the uncertainty of the phase-shift measurement can be reduced to the Heisenberg limit of 1/N (N is the total number of the photons in the input state) with certai n measurement schemes. (C) 1998 Elsevier Science B.V. All rights reser ved.