DENSITY-MATRIX RECONSTRUCTION BY UNBALANCED HOMODYNING

Recently a method for measuring quasidistributions of single-mode opti cal fields in unbalanced homodyne detection has been proposed [S. Wall entowitz and W. Vogel, Phys. Rev. A 53, 4528 (1996); K. Banaszek and K . Wodkiewicz, Phys. Rev. Lett. 76, 4344 (1996)]. We show that the sche me can be used for direct sampling of the signal-mode density matrix i n the Fock basis. In this case it is sufficient to vary only the phase of the local oscillator, keeping its amplitude constant.