7,402 research outputs found

    Quantum Interpretations

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    Difficulties and discomfort with the interpretation of quantum mechanics are due to differences in language between it and classical physics. Analogies to The Special Theory of Relativity, which also required changes in the basic worldview and language of non-relativistic classical mechanics, may help in absorbing the changes called for by quantum physics. There is no need to invoke extravagances such as the many worlds interpretation or specify a central role for consciousness or neural microstructures. The simple, but basic, acceptance that what is meant by the state of a physical system is different in quantum physics from what it is in classical physics goes a long way in explaining its seeming peculiarities.Comment: 13 page

    Non-Hermitian topology of spontaneous magnon decay

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    Spontaneous magnon decay is a generic feature of the magnetic excitations of anisotropic magnets and isotropic magnets with non-collinear order. In this paper, we argue that the effect of interactions on one-magnon states can, under many circumstances, be treated in terms of an effective, energy independent, non-Hermitian Hamiltonian for the magnons. In the vicinity of Dirac or Weyl touching points, we show that the spectral function has a characteristic anisotropy arising from topologically protected exceptional points or lines in the non-Hermitian spectrum. Such features can, in principle, be detected using inelastic neutron scattering or other spectroscopic probes. We illustrate this physics through a concrete example: a honeycomb ferromagnet with Dzyaloshinskii-Moriya exchange. We perform interacting spin wave calculations of the structure factor and spectral function of this model, showing good agreement with results from a simple effective non-Hermitian model for the splitting of the Dirac point. Finally, we argue that the zoo of known topological protected magnon band structures may serve as a nearly ideal platform for realizing and exploring non-Hermitian physics in solid-state systems.Comment: 4+epsilon page

    1, 2, and 6 qubits, and the Ramanujan-Nagell theorem

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    A conjecture of Ramanujan that was later proved by Nagell is used to show on the basis of matching dimensions that only three nn-qubit systems, for n=1,2,6n=1, 2, 6, can share an isomorphism of their symmetry groups with the rotation group of corresponding dimensions 3,6,913, 6, 91. Topological analysis, however, rules out the last possibility

    Complete time-dependent treatment of a three-level system

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    Both unitary evolution and the effects of dissipation and decoherence for a general three-level system are of widespread interest in quantum optics, molecular physics, and elsewhere. A previous paper presented a technique for solving the time-dependent operator equations involved but under certain restrictive conditions. We now extend our results to a general three-level system with arbitrary time-dependent Hamiltonians and Lindblad operators. Analytical handling of the SU(3) algebra of the eight operators involved leaves behind a set of coupled first-order differential equations for classical functions. Solution of this set gives a complete solution of the quantum problem, without having to invoke rotating-wave or other approximations. Numerical illustrations are given.Comment: 1 tar.gz file containing a Tex and four eps figure files; unzip with command gunzip RZPRA05.tar.g

    Recruiting Older Workers: Realities and Needs of the Future Workforce

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    This chapter examines literature pertaining to the recruitment of older workers. It begins by addressing the question of relevance and why older worker recruitment matters. It then examines what is known about older workers, including their attitudes, motivations, and behaviors. Next the chapter addresses what employers are looking for in older workers and, more specifically, discusses the continuum of employers’ practices from those that aggressively try to attract and retain older workers and apply a conservation model of older worker management to those that apply a depreciation model and focus primarily on retrenchment and downsizing older employees. Finally, it addresses how employers can recruit older workers through changes in organizational policies and practices

    Sudden change in dynamics of genuine multipartite entanglement of cavity-reservoir qubits

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    We study the dynamics of genuine multipartite entanglement for a system of four qubits. Using a computable entanglement monotone for multipartite systems, we investigate the as yet unexplored aspects of a cavity-reservoir system of qubits. For one specific initial state, we observe a sudden transition in the dynamics of genuine entanglement for the four qubits. This sudden change occurs only during a time window where neither cavity-cavity qubits nor reservoir-reservoir qubits are entangled. We show that this sudden change in dynamics of this specific state is extremely sensitive to white noise.Comment: 18 pages, 11 figure
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