Abstract
A unitary operator is defined, connecting the states of the measured system and the measuring-instrument system before and after interaction, by means of which the post-interaction values of in the instrument can be used to calculate the pre-interaction and in the measured system, where and are Hermitian operators. The premeasurement state of the instrument need not be known, and the same measurement operator is applicable whether the system to be measured is originally described by a pure case or a mixture. Finally, this theory is contrasted briefly with the measurement theory of von Neumann.
- Received 12 July 1962
DOI:https://doi.org/10.1103/PhysRev.129.940
©1963 American Physical Society