2009/06/23 by O. Brodier, Olivier Brodier, Alfredo M. Ozorio de Almeida +1
Computer Science · Mathematics · Physics and Astronomy · #Cold Atom Physics and Bose-Einstein Condensates #Hamiltonian (control theory) #Mathematical physics #Mathematics #Physics #Quantum #Quantum Information and Cryptography #Quantum Mechanics and Applications #Quantum decoherence #Quantum mechanics #Semiclassical physics #WKB approximation #quant-ph
paper · pdf · doi:10.1088/1751-8113/43/50/505308
16 pages
arxiv created 2009/06/23 · openalex publication_date 2010/11/25 · arxiv updated 2015/05/13 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
We derive a semiclassical approximation for the evolution generated by the Lindblad equation as a generalization of complex WKB theory. Linear coupling to the environment is assumed, but the Hamiltonian can be a general function of positions and momenta. The theory is carried out in the chord representation and describes the evolved quantum characteristic function, which gives direct access to the Wigner function and the position representation of the density operator by Fourier transforms. The propagation is shown to be of Liouville type in a complex double phase space, the imaginary part of the action being responsible for decoherence. The theory is exact in the quadratic case, just as the real WKB theory that we previously developed for the Markovian evolution of extended states, but it also describes the decoherent and dissipative evolution of localized states, such as the interference terms of a Schr"odinger cat state. The present rederivation of the real WKB approximation leads to its interpretation as a first order classical perturbation of the complex theory and to a discussion of its validity. The example of a simple cubic Hamiltonian illustrates the various levels of approximation derived from the complex WKB theory.