Meaning of the Density Matrix
Abstract
Description
Protective measurement, which was proposed as a method of observing the wavefunction of a single system, is extended to the observation of the density matrix of a single system. d'Espagnat's definition of `proper mixture' is shown to be improper because it does not allow for appropriate fluctuations. His claim that there could be different mixtures corresponding to the same density matrix is critically examined. These results provide a new meaning to the density matrix, which gives it the same ontological status as the wavefunction describing a pure state. This also enables quantum entropy to be associated with a single system.
12 pages, latex, no figures, paper presented at the International Symposium on UNCERTAIN REALITY, New Delhi, India, Jan. 5-9, 1998
12 pages, latex, no figures, paper presented at the International Symposium on UNCERTAIN REALITY, New Delhi, India, Jan. 5-9, 1998