共查询到20条相似文献,搜索用时 9 毫秒
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Sylvia Pulmannová 《Communications in Mathematical Physics》1976,49(1):47-51
A new definition of the superposition principle in quantum logics is given, which enables us to define the sectors. It is shown that the superposition principle holds only in the irreducible quantum logics. 相似文献
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We study the dynamical symmetries of a class of two-dimensional superintegrable systems on a 2-sphere, obtained by a procedure
based on the Marsden-Weinstein reduction, by considering its shape-invariant intertwining operators. These are obtained by
generalizing the techniques of factorization of one-dimensional systems. We firstly obtain a pair of noncommuting Lie algebras
su(2) that originate the algebra so(4). By considering three spherical coordinate systems, we get the algebra u(3) that can be enlarged by “reflexions” to so(6). The bounded eigenstates of the Hamiltonian hierarchies are associated to the irreducible unitary representations of these
dynamical algebras.
The text was submitted by the authors in English. 相似文献
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There are four reasons why our present knowledge and understanding of quantum mechanics can be regarded as incomplete. (1)
The principle of linear superposition has not been experimentally tested for position eigenstates of objects having more than
about a thousand atoms. (2) There is no universally agreed upon explanation for the process of quantum measurement. (3) There
is no universally agreed upon explanation for the observed fact that macroscopic objects are not found in superposition of
position eigenstates. (4) Most importantly, the concept of time is classical and hence external to quantum mechanics: there
should exist an equivalent reformulation of the theory which does not refer to an external classical time. In this paper we
argue that such a reformulation is the limiting case of a nonlinear quantum theory, with the nonlinearity becoming important
at the Planck mass scale. Such a nonlinearity can provide insights into the aforesaid problems. We use a physically motivated
model for a nonlinear Schr?dinger equation to show that nonlinearity can help in understanding quantum measurement. We also
show that while the principle of linear superposition holds to a very high accuracy for atomic systems, the lifetime of a
quantum superposition becomes progressively smaller, as one goes from microscopic to macroscopic objects. This can explain
the observed absence of position superpositions in macroscopic objects (lifetime is too small). It also suggests that ongoing
laboratory experiments may be able to detect the finite superposition lifetime for mesoscopic objects in the near future. 相似文献
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Brownstein KR 《Physical review letters》1993,71(9):1427-1430
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J. Gough 《Russian Journal of Mathematical Physics》2014,21(3):337-347
In this paper, we formulate limit Zeno dynamics of general open systems as the adiabatic elimination of fast components. We are able to exploit previous work on adiabatic elimination of quantum stochastic models to give explicitly the conditions under which open Zeno dynamics will exist. The open systems formulation is further developed as a framework for Zeno master equations, and Zeno filtering (that is, quantum trajectories based on a limit Zeno dynamical model). We discuss several models from the point of view of quantum control. For the case of linear quantum stochastic systems, we present a condition for stability of the asymptotic Zeno dynamics. 相似文献
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Master equations without Lindblad form can in principle violate the positivity of the density operator. However, when such a master equation arises through systematic adiabatic elimination of fast variables from underlying microscopic dynamics, the violation can at worst arise on time scales one has coarsegrained over when performing the adiabatic elimination and can thus simply be ignored. Examples of non-Lindblad master equations are shown to arise for the Ornstein Uhlenbeck process both at high and low temperatures and for a single-mode laser operated near threshold. 相似文献
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We consider open quantum systems weakly coupled to a heat reservoir and driven by arbitrary time-dependent parameters. We derive exact microscopic expressions for the nonequilibrium entropy production and entropy production rate, valid arbitrarily far from equilibrium. By using the two-point energy measurement statistics for system and reservoir, we further obtain a quantum generalization of the integrated fluctuation theorem put forward by Seifert [Phys. Rev. Lett. 95, 040602 (2005)]. 相似文献
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《Physics letters. [Part B]》1988,206(2):343-345
We suggest a method of searching for small violations of the Pauli principle. It is based on extracting and counting atoms with wrong (excessive) filling of the electron shells. Our estimates show that this approach proves to be several orders of magnitude more effective than the search for Pauli-forbidden X-ray transitions in NaJ (Tl) crystal. 相似文献
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We show that a dissipative current component is present in the dynamics generated by a Liouville-master equation, in addition to the usual component associated with Hamiltonian evolution. The dissipative component originates from coarse graining in time, implicit in a master equation, and needs to be included to preserve current continuity. We derive an explicit expression for the dissipative current in the context of the Markov approximation. Finally, we illustrate our approach with a simple numerical example, in which a quantum particle is coupled to a harmonic phonon bath and dissipation is described by the Pauli master equation. 相似文献
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The degree of entanglement in an open quantum system varies according to how information in the environment is read. A measure of this contextual entanglement is introduced based on quantum trajectory unravelings of the open system dynamics. It is used to characterize the entanglement in a driven quantum system of dimension 2 x infinity where the entanglement is induced by the environmental interaction. A detailed mechanism for the environment-induced entanglement is given. 相似文献
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Jens Hoppe Michail Olshanetsky Stefan Theisen 《Communications in Mathematical Physics》1993,155(3):429-448
We use quantum tori Lie algebras (QTLA), which are a one-parameter family of sub-algebras ofgl
, to describe local and non-local versions of the Toda systems. It turns out that the central charge of QTLA is responsible for the non-locality. There are two regimes in the local systems-conformal for irrational values of the parameter and non-conformal and integrable for its rational values. We also consider infinite-dimensional analogs of rigid tops. Some of these systems give rise to quantized (magneto-)hydrodynamic equations of an ideal fluid on a torus. We also consider infinite dimensional versions of the integrable Euler and Clebsch cases. 相似文献
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《Physica D: Nonlinear Phenomena》2001,148(3-4):227-241
Departing from classical concepts of ergodic theory, formulated in terms of probability densities, measures describing the mixing behavior and the loss of information in quantum open systems are proposed. As application we discuss the chaotic outcomes of continuous measurement processes in the EEQT framework. Simultaneous measurement of four noncommuting spin components is shown to lead to a chaotic jumps on the quantum spin sphere and to generate specific fractal images of a nonlinear iterated function system. 相似文献
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《Physics letters. A》2019,383(15):1698-1710
In this work, we present a multiple-scale perturbation technique suitable for the study of open quantum systems, which is easy to implement and in few iterative steps allows us to find excellent approximate solutions. For any time-local quantum master equation, whether markovian or non-markovian, in Lindblad form or not, we give a general procedure to construct analytical approximations to the corresponding dynamical map and, consequently, to the temporal evolution of the density matrix. As a simple illustrative example of the implementation of the method, we study an atom-cavity system described by a dissipative Jaynes-Cummings model. Performing a multiple-scale analysis we obtain approximate analytical expressions for the strong and weak coupling regimes that allow us to identify characteristic time scales in the state of the physical system. 相似文献
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The notion of a nonlinear quantum dynamical semigroup is introduced, and the existence and uniqueness of solutions of the corresponding nonlinear evolution equations are studied in a more abstract framework. The construction of nonlinear quantum dynamical semigroups is carried out for two different mean-field models. First a mean-field coupling between a system of noninteracting subsystems and the bath is investigated. As examples, a nonlinear frictional Schrödinger equation and a model for a quantum Boltzmann equation are discussed. Second, a many-body system with mean-field interaction coupled to a bath is considered. Here, again, the form of the generator is derived; however, it cannot be obtained rigorously, except for some particular examples. Finally, the quantum Ising-Weiss model is briefly studied. 相似文献