posted on 2021-11-10, 18:36authored byAmro Dodin, Adam P. Willard
We develop a nonequilibrium response
theory for macroscopic quantum
systems that separates the contributions of ensemble heterogeneity
and intrinsic quantum uncertainty. To accomplish this, we describe
systems with a quantum P-ensemble, which goes beyond
the standard density matrix description by explicitly specifying the
classical heterogeneity between individual quantum systems in an ensemble.
We use the P-ensemble formalism to present quantum
generalizations of linear response theory and the Jarzynski nonequilibrium
work relation. We derive these generalizations from a Bochkov-Kuzovlev
generating functional for quantum P-ensembles, which
can be further utilized to derive all orders of response theory that
apply to ensemble quantum systems. We contrast these developments
with their ρ-ensemble analogs, and we discuss how these P-ensemble theories provide a guide for an effective application
of single molecule experiments.