Decay of a coherent state in the interaction representation

眞治 前段

S. T.

G Lang, E Paladino, U Weiss

We study the equilibrium correlation function of the polaron-dressed tunnelling operator in the dissipative two-state system and compare the asymptoptic dynamics with that of the position correlations. For an Ohmic spectral density with damping strength K = ½, the correlation functions are obtained in analytic form for all times at any T and any bias. For K < 1, the asymptotic dynamics is found by using a diagrammatic approach within a Coulomb gas representation. At T = 0, the tunnelling or coherence correlations drop as t −2 K , whereas the position correlations show universal decay ∝ t −2 . The former decay law is a signature of unscreened attractive charge-charge interactions, while the latter is due to unscreened dipole-dipole interactions.

G. Reents, Stephen J. Summers

Weifeng Wu, Yong Hui Fang, Peng Fei Fu

Abstract Using the operator correspondence of the real and fictious modes in the thermo entangled state representation, we solve the quantum master equation describing the diffusion channel and obtain the Kraus operator-sum representation of its analytical solution. we find that the pure coherent states evolve into the new mixed thermal superposed states in the diffusion channel. Also, we investigate the statistical properties of the initial coherent states and their entropy evolutions in the diffusion channel, and find that the entropy evolutions are only related to the decay time and without the amplitudes of the initial coherent states.

James S. Langer

It is shown that the coherent-state representation of a many-boson wave function may be identified with the order-parameter function conventionally used to describe a superfluid. The statistical mechanics of the many-boson system is reformulated in terms of the coherent states, and a theory of the Ginzburg-Landau form is recovered in an obvious approximation. The formalism is particularly useful for describing metastable states of finite superflow and the fluctuations which may cause spontaneous decay of such states.