Narrow Results

We study dissipative dynamics constructed by means of non-commutative Dirichlet forms for various lattice systems with multiparticle interactions associated to CCR algebras. We give a number of explicit examples of such models. Using an idea of quasi-invariance of a state, we show how one can construct unitary representations of various groups. Moreover in models with locally conserved quantities associated to an infinite lattice we show that there is no spectral gap and the corresponding dissipative dynamics decay to equilibrium polynomially in time.

We show how to write a set of brackets for the Langevin equation, describing the dissipative motion of a classical particle, subject to external random forces. The method does not rely on an action principle, and is based solely on the phenomenological description of the dissipative dynamics as given by the Langevin equation. The general expression for the brackets satisfied by the coordinates, as well as by the external random forces, at different times, is determined, and it turns out that they all satisfy the Jacobi identity. Upon quantization, these classical brackets are found to coincide with the commutation rules for the quantum Langevin equation, that have been obtained in the past, by appealing to microscopic conservative quantum models for the friction mechanism.

We study the stability of breather solutions of a dissipative cubic discrete NLS with localized forcing. The breathers are similar to the ones found for the Hamiltonian limit of the system. In the case of linearly stable multi-peak breathers the combination of dissipation and localized forcing also leads to stability, and the apparent damping of internal modes that make the energy around multi-peak breathers nondefinite. This stabilizing effect is however accompanied by overdamping for relatively small values of the dissipation parameter, and the appearance of near-zero stable eigenvalues.

We present a theoretical scheme for achieving the field-free molecular orientation in dissipative media by a combination of femtosecond and THz laser pulses. Numerical calculations are performed by solving the quantum Liouville equation based on multilevel Bloch model. The molecular orientation degree is sensitive to the carrier-envelope phase of the THz pulse and the delay time between the two pulses. The orientation and the rotational population of CO molecules in dissipative environment are computed at different pressures and temperatures. The influence of pure decoherence on the molecular orientation is also discussed.

Non-positive, Markovian semigroups are sometimes used to describe the time evolution of subsystems immersed in an external environment. A widely adopted prescription to avoid the appearance of negative probabilities is to eliminate from the admissible initial conditions those density matrices that would not remain positive by the action of the semigroup dynamics. Using a continuous variable model, we show that this procedure leads to physical inconsistencies when two subsystems are considered and their initial state is entangled.

No abstract received.

In the evolution of a quantum system subject to a nonlinear dissipative term of Kostin type the probability amplitudes associated to excited states of the Hamiltonian are damped; this results in a dynamic convergence toward the ground state. In this paper we dicuss how dissipation can replace adiabatic evolution in the search of the ground state of a target Hamiltonian and discuss applications to Quantum Annealing.

The momentum dependence of dissipation in heavy-ion reactions is studied. Special attention is paid to the dissipation due to the spin-orbit and spincurrent tensor contributions in the Skyrme energy-density functional formalism. The spin polarization, which brings about large dissipation in the early stage of heavy-ion reactions, mainly arises from those two contributions.

Entanglement between two quantum systems is a resource in quantum information, but dissipation usually destroys it. In this article we consider two qubits without direct interaction. We show that, even in cases where the entanglement is destroyed by the open system dynamics, the entanglement can be preserved or created by the mere monitoring of the environment, just by filtering the state of the qubits. While the systems we study are very simple, we can show examples with entanglement protection or entanglement birth, death, rebirth due to monitoring.