SIMPLE REALIZATIONS OF GENERALIZED MEASUREMENTS IN QUANTUM-MECHANICS

This paper discusses the approach to the analysis of measurements in q uantum mechanics which is based on a set of ''detection operators'' fo rming a resolution of identity. The expectation value of each of these operators furnishes the counting rate at a detector for any object st ate that is prepared. ''Predictable measurements'' are those for which there is a representation in which only one element of each diagonal matrix representing each operator is not zero. A set of commuting dete ction operators defines the class of ''spectral measurements'', which may be either predictable or not. An even more general definition of m easurement may be given by abandoning the requirement of commutativity of the detection operators. In this case one cannot define an observa ble which corresponds to a single self-adjoint operator, which violate s the standard theory of quantum mechanical measurement. Simple experi mental realizations of each of these classes of measurement are sugges ted.