ABSTRACT

The uncontrollable disturbance attendant upon a measurement implies that the act of measurement is indivisible. Any attempt to trace the history of a system during a measurement process usually changes the nature of the measurement that is being performed. Hence, to conceive of a given selective measurement M(a', b') as a compound measurement is without physical implication. All algebraic relations and adjoint connections among vectors and operators are preserved by unitary transformation. Two successive unitary transformations form a unitary transformation, and the inverse of a unitary transformation is unitary-unitary transformations form a group. In discussing successive unitary transformations, it must be recognized that a transformation which is specified by an array of numerical coefficients is symbolized by a unitary operator that depends upon the coordinate system to which it is applied. The continual repetition of an infinitesimal unitary transformation generates a finite unitary transformation.