The dynamical role of initial correlation in the exactly solvable dephasing model

We investigate the effects of the initial correlation on the dynamics of open system in the exactly solvable pure dephasing model. We show that the role of the initial correlation come into play through a phase function and a weight factor, which would perform oscillations during time evolution, and find that the decoherence of a qubit coupled to a boson bath is more enhanced with respect to a spin bath in the short time. We also demonstrate that the trace distance between two states of a qubit can increase above its initial value, and that the initial correlation can provide another resource for the damply oscillation and revival of the entanglement of two qubits. We finally investigate the dependence of the crossover of decoherence from the dynamical enhancement to suppression under the bang-bang pulse control on the initial correlation and the statistics of the bath constituents.Comment: revised final versio

Second order semiclassical theory of Bloch electrons in uniform electromagnetic fields

textBerry curvature appears in the semi-classical theory of Bloch electrons already to first order in electromagnetic fields, resulting in profound modification of the carrier velocity and phase space density of states. Here we derive the equations of motion for the physical position and crystal momentum to second order in the fields. The dynamics still has a Hamiltonian structure, albeit with noncanonical Poisson brackets between the physical variables. We are able to expand both the carrier energy and the Poisson brackets to second order in the fields with terms of clear physical meaning. To demonstrate the utility of our theory, we obtain with much ease the electromagnetic response and orbital magnetic susceptibility.Physic