Operational approach to phase-space measurements in quantum mechanics

Wódkiewicz1 has derived an operational formula for a positive phase-space distribution function in quantum mechanics (see also ref. 2). Here we point out that the proposed formula is actually a special case of a two-particle Wigner distribution function in which correlations have been neglected. We present a new operational formula which includes correlations. Also, we incorporate a brief description of the role and significance of quantum distribution functions in general. © 1984 Nature Publishing Group