160 research outputs found
Quantum jumps and entropy production
The irreversible motion of an open quantum system can be represented through
an ensemble of state vectors following a stochastic dynamics with piecewise
deterministic paths. It is shown that this representation leads to a natural
definition of the rate of quantum entropy production. The entropy production
rate is expressed in terms of the von Neumann entropy and of the numbers of
quantum jumps corresponding to the various decay channels of the open system.
The proof of the positivity and of the convexity of the entropy production rate
is given. Monte Carlo simulations of the stochastic dynamics of a driven qubit
and of a -configuration involving a dark state are performed in order
to illustrate the general theory.Comment: 7 pages, 2 figure
The non-Markovian quantum behavior of open systems: An exact Monte Carlo method employing stochastic product states
It is shown that the exact dynamics of a composite quantum system can be
represented through a pair of product states which evolve according to a
Markovian random jump process. This representation is used to design a general
Monte Carlo wave function method that enables the stochastic treatment of the
full non-Markovian behavior of open quantum systems. Numerical simulations are
carried out which demonstrate that the method is applicable to open systems
strongly coupled to a bosonic reservoir, as well as to the interaction with a
spin bath. Full details of the simulation algorithms are given, together with
an investigation of the dynamics of fluctuations. Several potential
generalizations of the method are outlined.Comment: 14 pages, 5 figure
Quantum Semi-Markov Processes
We construct a large class of non-Markovian master equations that describe
the dynamics of open quantum systems featuring strong memory effects, which
relies on a quantum generalization of the concept of classical semi-Markov
processes. General conditions for the complete positivity of the corresponding
quantum dynamical maps are formulated. The resulting non-Markovian quantum
processes allow the treatment of a variety of physical systems, as is
illustrated by means of various examples and applications, including quantum
optical systems and models of quantum transport.Comment: 4 pages, revtex, no figures, to appear in Phys. Rev. Let
Revealing correlations between a system and an inaccessible environment
How can we detect that our local, controllable quantum system is correlated
with some other inaccessible environmental system? The local detection method
developed in recent years allows to realize a dynamical witness for
correlations without requiring knowledge of or access to the environment that
is correlated with the local accessible quantum system. Here, we provide a
brief summary of the theoretical method and recent experimental studies with
single photons and trapped ions coupled to increasingly complex environments.Comment: 12 pages, 3 figure
Structure of completely positive quantum master equations with memory kernel
Semi-Markov processes represent a well known and widely used class of random
processes in classical probability theory. Here, we develop an extension of
this type of non-Markovian dynamics to the quantum regime. This extension is
demonstrated to yield quantum master equations with memory kernels which allow
the formulation of explicit conditions for the complete positivity of the
corresponding quantum dynamical maps, thus leading to important insights into
the structural characterization of the non-Markovian quantum dynamics of open
systems. Explicit examples are analyzed in detail.Comment: 13 pages, revtex, 2 figure
Concepts and methods in the theory of open quantum systems
The central physical concepts and mathematical techniques used in the theory
of open quantum systems are reviewed. Particular emphasis is laid on the
interrelations of apparently different approaches. Starting from the
appropriate characterization of the quantum statistical ensembles naturally
arising in the description of open quantum systems, the corresponding dynamical
evolution equations are derived for the Markovian as well as for the
non-Markovian case.Comment: 15 pages, 7 figures, conference proceedings, to be published in:
Irreversible Quantum Dynamics, Lecture Notes in Physics, F. Benatti and R.
Floreanini (Eds
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