53 research outputs found
Quantum stochastic equation for the low density limit
A new derivation of quantum stochastic differential equation for the
evolution operator in the low density limit is presented. We use the
distribution approach and derive a new algebra for quadratic master fields in
the low density limit by using the energy representation. We formulate the
stochastic golden rule in the low density limit case for a system coupling with
Bose field via quadratic interaction. In particular the vacuum expectation
value of the evolution operator is computed and its exponential decay is shown.Comment: Replaced with version published in J. Phys. A. References are adde
Quantum feedback control in quantum photosynthesis
A model of charge separation in quantum photosynthesis as a model of quantum
feedback control in a system of interacting excitons and vibrons is introduced.
Quantum feedback in this approach describes the Landau--Zener transition with
decoherence. The model explains irreversibility in the process of charge
separation for quantum photosynthesis -- direct transitions for this quantum
control model will have probabilities close to one and reverse transitions will
have probabilities close to zero. This can be considered as a model of quantum
ratchet. Also this model explains coincidence of energy of the vibron paired to
the transition and Bohr frequency of the transition.Comment: 10 pages, commentaries adde
A stochastic golden rule and quantum Langevin equation for the low density limit
A rigorous derivation of quantum Langevin equation from microscopic dynamics
in the low density limit is given. We consider a quantum model of a microscopic
system (test particle) coupled with a reservoir (gas of light Bose particles)
via interaction of scattering type. We formulate a mathematical procedure (the
so-called stochastic golden rule) which allows us to determine the quantum
Langevin equation in the limit of large time and small density of particles of
the reservoir. The quantum Langevin equation describes not only dynamics of the
system but also the reservoir. We show that the generator of the corresponding
master equation has the Lindblad form of most general generators of completely
positive semigroups
- …