Theorie Kolloquium | June 30, 16:30
Grand canonical Gibbs state for systems with non-commuting charges
The grand canonical ensemble lies at the core of quantum and classical
statistical mechanics. A small system thermalizes to this ensemble while
exchanging heat and particles with a bath. A quantum system may exchange
quantities represented by operators that fail to commute. Whether such
a system thermalizes and what form the thermal state has are questions
about truly quantum thermodynamics. Here we investigate this thermal
state from three perspectives. First, we introduce an approximate
microcanonical ensemble. If this ensemble characterizes the system-
and-bath composite, tracing out the bath yields the system's thermal
state. This state is expected to be the equilibrium point, we argue,
of typical dynamics. Finally, we define a resource-theory model for
thermodynamic exchanges of noncommuting observables. Complete passivity
-- the inability to extract work from equilibrium states -- , implies
the thermal state's form, too. Our work opens new avenues into
equilibrium in the presence of quantum noncommutation.
[Based on arXiv:1512.01189]
Universitat Autònoma de Barcelona
SR 0.03 TP
Contact: David Gross