On the correspondence principle : implications from a study of the nonlinear dynamics of a macroscopic quantum device
Mark Everitt (1250502)
Abstract
The recovery of classical nonlinear and chaotic dynamics from\nquantum systems has long been a subject of interest. Furthermore, recent work\nindicates that quantum chaos may well be significant in quantum information\nprocessing. In this paper, we discuss the quantum to classical crossover of\na superconducting quantum interference device (SQUID) ring. Such devices\ncomprise a thick superconducting loop enclosing a Josephson weak link and are\ncurrently strong candidates for many applications in quantum technologies. The\nweak link brings with it a nonlinearity such that semiclassical models of this\nsystem can exhibit nonlinear and chaotic dynamics. For many similar systems\nan application of the correspondence principle together with the inclusion of\nenvironmental degrees of freedom through a quantum trajectories approach can\nbe used to effectively recover classical dynamics. Here we show (i) that the\nstandard expression of the correspondence principle is incompatible with the\nring Hamiltonian and we present a more pragmatic and general expression which\nfinds application here and (ii) that practical limitations to circuit parameters\nof the SQUID ring prevent arbitrarily accurate recovery of classical nonlinear\ndynamics.