Littérature scientifique sur le sujet « Lindblad-Form »

The quantum damped harmonic oscillator is described by the master equation with usual Lindblad form. The equation has been solved completely by us in arXiv: 0710.2724 [quant-ph]. To construct the general solution a few facts of representation theory based on the Lie algebra su(1,1) were used. In this paper we treat a general model described by a master equation with generalized Lindblad form. Then we examine the algebraic structure related to some Lie algebras and construct the interesting approximate solution.

We prove energy estimates for a relativistic free liquid body with sufficiently small fluid velocity in a general Lorentz spacetime. These estimates control Sobolev norms of the fluid velocity and enthalpy in the interior as well as Sobolev norms of the second fundamental form on the boundary. These estimates are generalizations of the energy estimates of Christodoulou and Lindblad [D. Christodoulou and H. Lindblad, On the motion of the free surface of a liquid, Commun. Pure Appl. Math. 53(12) (2000) 1536–1602] and rely on elliptic estimates which only require bounds for the second fundamental form of the time slices of the free boundary.

Fermionic linear optics is a limited form of quantum computation which is known to be efficiently simulable on a classical computer. We revisit and extend this result by enlarging the set of available computational gates: in addition to unitaries and measurements, we allow dissipative evolution governed by a Markovian master equation with linear Lindblad operators. We show that this more general form of fermionic computation is also simulable efficiently by classical means. Given a system of $N$~fermionic modes, our algorithm simulates any such gate in time $O(N^3)$ while a single-mode measurement is simulated in time $O(N^2)$. The steady state of the Lindblad equation can be computed in time $O(N^3)$.

We study the nonlinear quantum master equation describing a laser under the mean field approximation. The quantum system is formed by a single mode optical cavity and two level atoms, which interact with reservoirs. Namely, we establish the existence and uniqueness of the regular solution to the nonlinear operator equation under consideration, as well as we get a probabilistic representation for this solution in terms of a mean field stochastic Schrödinger equation. To this end, we find a regular solution for the nonautonomous linear quantum master equation in Gorini–Kossakowski–Sudarshan–Lindblad form, and we prove the uniqueness of the solution to the nonautonomous linear adjoint quantum master equation in Gorini–Kossakowski–Sudarshan–Lindblad form. Moreover, we obtain rigorously the Maxwell–Bloch equations from the mean field laser equation.

This paper deals with the asymptotic behavior of a quantum dynamical semigroup [Formula: see text] acting on the algebra of all linear bounded operators on a given Hilbert space. In practice, all these semigroups have a generator which can be written in a well-known form named after Lindblad and Davies. If the semigroup has a faithful normal stationary state ρ, necessary and sufficient conditions are derived for the w*-convergence of [Formula: see text] to [Formula: see text], where [Formula: see text] is the conditional expectation of an element X onto the subalgebra of fixed points. Our main results are expressed in terms of the Lindblad–Davies generator .

We study the dynamics of four-qubit W state under various noisy environments by solving analytically the master equation in the Lindblad form in which the Lindblad operators correspond to the Pauli matrices and describe the decoherence of states. Also, we investigate the dynamics of the entanglement using the lower bound to the concurrence. It is found that while the entanglement decreases monotonically for Pauli-Z noise, it decays suddenly for other three noises. Moreover, by studying the time evolution of entanglement of various maximally entangled four-qubit states, we indicate that the four-qubit W state is more robust under same-axis Pauli channels. Furthermore, three-qubit W state preserves more entanglement with respect to the four-qubit W state, except for the Pauli-Z noise.

In quantum systems theory one of the fundamental problems boils down to: given an initial state, which final states can be reached by the dynamic system in question. Here we consider infinite-dimensional open quantum dynamical systems following a unital Kossakowski–Lindblad master equation extended by controls. More precisely, their time evolution shall be governed by an inevitable potentially unbounded Hamiltonian drift term H0, finitely many bounded control Hamiltonians Hj allowing for (at least) piecewise constant control amplitudes [Formula: see text] plus a bang-bang (i.e., on-off) switchable noise term ГV in Kossakowski–Lindblad form. Generalizing standard majorization results from finite to infinite dimensions, we show that such bilinear quantum control systems allow to approximately reach any target state majorized by the initial one as up to now it only has been known in finite dimensional analogues. The proof of the result is currently limited to the bounded control Hamiltonians Hj and for noise terms ГV with compact normal V.

In der vorliegenden Arbeit werden Untersuchungen vorgestellt, die sich mit drei verschiedenen Aspekten der Dynamik offener Quantensysteme beschäftigen. Zwei Themenkreise haben dabei mehr grundsätzliche Probleme der Theorie dissipativer Molekularsysteme zum Gegenstand. Dementsprechend müssen die Betrachtungen dazu auf einem allgemeineren Niveau verbleiben. In dem dritten Themenkreis jedoch, der sich mit Zwei-Teilchen-Effekten in der dissipativen Dynamik befaßt, können die Untersuchungen bis hin zu Berechnung von Meßgrößen geführt werden. Im ersten Teil der Arbeit gelingt eine Verallgemeinerung der vielbenutzten Standardform der Quanten-Master-Gleichung hin zur Nichtlinearen Quanten-Master-Gleichung. Mit der Anwendung der dazugehörigen zeitabhängigen Projektionsoperator-Technik kann ein Formalismus reaktiviert werden, der in der Literatur bisher eine nur sehr eingeschränkte Verbreitung findet. Der zweite Teil der Arbeit widmet sich Untersuchungen zur Monte-Carlo-Wellenfunktions-Methode mit dem Ergebnis, eine konsistente Verallgemeinerung auf ein Reservoir mit endlicher Temperatur anzugeben. Den Ausgangspunkt dazu bildet ein mikroskopisches Modell zur System-Reservoir-Kopplung, welches im Rahmen der Bewegungsgleichung für den reduzierten statistischen Operator in die sogenannte Lindblad-Form der Dissipation überführt wird. Nach der Betrachtung von Ein-Teilchen-Transferprozessen beschäftigt sich der dritte Teil der Arbeit mit der korrelierten Bewegung von zwei Quantenteilchen in einer dissipativen Umgebung mit der Hinwendung zum Zwei-Wasserstoff-System (Dihydrid-System) an Übergangsmetall-Verbindungen. Zunächst werden Modellrechnungen zur dissipationfreien Zwei-Teilchen-Dynamik in einem Potentialmodell durchzuführt. Der Einfluß, den die Teilchen-Teilchen-Korrelationen auf das Durchtunneln eines Potentialwalles besitzt, können durch verschiedene numerische Rechnungen aufgezeigt werden. Wie sich diese Effekte in Neutronenstreuexperimenten an dem Zwei-Teilchen-System der Übergangsmetall-Hydrid-Komplexe äußern, wird basierend auf Simulationsrechnungen untersucht. Kernstück dieser Betrachtungen bildet eine neuartige Formel für die Neutronenstreuung, die auf der dissipativen Dynamik des betrachteten Zwei-Teilchen-Systems aufbaut.
In the report at hand studies are presented dealing with three differentaspects of the dynamics of open quantum systems. Two topics are about the fundamental problems of the theory of dissipative molecular systems. Accordingly these investigations must remain on a more general level. In the third subject, however, which is about the two-particle effects in the dissipative dynamics the analyses can be extended to the computation of measurements. In the first part of the report a generalization of the well known standard quantum master equation to the nonlinear quantum master equation is developed. With the help of the projection operator technique belonging to it a formalism, that has not been popular in literature so far, can be reactivated. The second part of the report concentrates on examinations of the Monte-Carlo wave-function method, and results in the consistent generalization for a reservoir of finite temperature. The starting point for this is a microscopic model of the system-reservoir coupling, which is expanded to the so called Lindblad form of the dissipation in the line of the equation of motion for the reduced statistical operator. After the analysis of one-particle transfer processes the third part of the report is about the correlated motion of two quantum particles in a dissipative environment with main emphasis on the two-hydrogen system (dihydrid system) in transition metal complexes. First of all model computations for the dissipationless two-particle dynamics in a potential model are made. By different numerical computations the influence, which the particle-particle correlations exert on the tunneling through a potential barrier, can be shown.Based on simulations it is examined how these effects can be seen in neutron scattering experiments on two-particle systems of transition metal complexes. Main item of these investigations is a new formula for the neutron scattering which is based on the dissipative dynamics of the examined two-particle system.

In this chapter we study with the tools developed in Chapter 3 the basic models that are the foundations of light–matter interaction. We start with Rabi dynamics, then consider the optical Bloch equations that add phenomenologically the lifetime of the populations. As decay and pumping are often important, we cover the Lindblad form, a correct, simple and powerful way to describe various dissipation mechanisms. Then we go to a full quantum picture, quantizing also the optical field. We first investigate the simpler coupling of bosons and then culminate with the Jaynes–Cummings model and its solution to the quantum interaction of a two-level system with a cavity mode. Finally, we investigate a broader family of models where the material excitation operators differ from the ideal limits of a Bose and a Fermi field.