Koopman wavefunctions and classical–quantum correlation dynamics

Denys I. Bondar, François Gay-Balmaz, Cesare Tronci
2019 Proceedings of the Royal Society A  
Upon revisiting the Hamiltonian structure of classical wavefunctions in Koopman-von Neumann theory, this paper addresses the long-standing problem of formulating a dynamical theory of classical-quantum coupling. The proposed model not only describes the influence of a classical system onto a quantum one, but also the reverse effect-the quantum backreaction. These interactions are described by a new Hamiltonian wave equation overcoming shortcomings of currently employed models. For example, the
more » ... ensity matrix of the quantum subsystem is always positive definite. While the Liouville density of the classical subsystem is generally allowed to be unsigned, its sign is shown to be preserved in time for a specific infinite family of hybrid classical-quantum systems. The proposed description is illustrated and compared with previous theories using the exactly solvable model of a degenerate two-level quantum system coupled to a classical harmonic oscillator.
doi:10.1098/rspa.2018.0879 pmid:31611710 pmcid:PMC6784396 fatcat:k3qyeoweovfjfo7t76t55xeb7e