Abstract
For a macroscopic, isolated quantum system in an unknown pure state, the expectation value of any given observable is shown to hardly deviate from the ensemble average with extremely high probability under generic equilibrium and nonequilibrium conditions. Special care is devoted to the uncontrollable microscopic details of the system state. For a subsystem weakly coupled to a large heat bath, the canonical ensemble is recovered under much more general and realistic assumptions than those implicit in the usual microcanonical description of the composite system at equilibrium.
- Received 17 July 2007
- Publisher error corrected 17 March 2008
DOI:https://doi.org/10.1103/PhysRevLett.99.160404
©2007 American Physical Society
Corrections
17 March 2008