77,022 research outputs found
Universality of spectra for interacting quantum chaotic systems
We analyze a model quantum dynamical system subjected to periodic interaction
with an environment, which can describe quantum measurements. Under the
condition of strong classical chaos and strong decoherence due to large
coupling with the measurement device, the spectra of the evolution operator
exhibit an universal behavior. A generic spectrum consists of a single
eigenvalue equal to unity, which corresponds to the invariant state of the
system, while all other eigenvalues are contained in a disk in the complex
plane. Its radius depends on the number of the Kraus measurement operators, and
determines the speed with which an arbitrary initial state converges to the
unique invariant state. These spectral properties are characteristic of an
ensemble of random quantum maps, which in turn can be described by an ensemble
of real random Ginibre matrices. This will be proven in the limit of large
dimension.Comment: 11 pages, 10 figure
Generalized Quantum Dynamics as Pre-Quantum Mechanics
We address the issue of when generalized quantum dynamics, which is a
classical symplectic dynamics for noncommuting operator phase space variables
based on a graded total trace Hamiltonian , reduces to Heisenberg
picture complex quantum mechanics. We begin by showing that when , with a Weyl ordered operator Hamiltonian, then the generalized
quantum dynamics operator equations of motion agree with those obtained from
in the Heisenberg picture by using canonical commutation relations. The
remainder of the paper is devoted to a study of how an effective canonical
algebra can arise, without this condition simply being imposed by fiat on the
operator initial values. We first show that for any total trace Hamiltonian
which involves no noncommutative constants, there is a conserved
anti--self--adjoint operator with a structure which is closely
related to the canonical commutator algebra. We study the canonical
transformations of generalized quantum dynamics, and show that is a
canonical invariant, as is the operator phase space volume element. The latter
result is a generalization of Liouville's theorem, and permits the application
of statistical mechanical methods to determine the canonical ensemble governing
the equilibrium distribution of operator initial values. We give arguments
based on a Ward identity analogous to the equipartition theorem of classical
statistical mechanics, suggesting that statistical ensemble averages of Weyl
ordered polynomials in the operator phase space variables correspond to the
Wightman functions of a unitary complex quantum mechanics, with a conserved
operator Hamiltonian and with the standard canonical commutation relations
obeyed by Weyl ordered operator strings. Thus there is a well--defined sense inComment: 79 pages, no figures, plain te
Rare-Event Sampling: Occupation-Based Performance Measures for Parallel Tempering and Infinite Swapping Monte Carlo Methods
In the present paper we identify a rigorous property of a number of
tempering-based Monte Carlo sampling methods, including parallel tempering as
well as partial and infinite swapping. Based on this property we develop a
variety of performance measures for such rare-event sampling methods that are
broadly applicable, informative, and straightforward to implement. We
illustrate the use of these performance measures with a series of applications
involving the equilibrium properties of simple Lennard-Jones clusters,
applications for which the performance levels of partial and infinite swapping
approaches are found to be higher than those of conventional parallel
tempering.Comment: 18 figure
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