Identification and Distance Measures of Measurement Apparatus

Abstract

We propose simple schemes that can perfectly identify projective measurement apparatus secretly chosen from a finite set. Entanglements are used in these schemes both to make possible the perfect identification and to improve the efficiency significantly. A brief discussion on the problem of how to appropriately define distance measures of measurements is also provided based on the results of identification.

5 pages, RevTeX, 1 figure. Revised version with more examples and a reorganization of the contents