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There seems to me to be a way of reading some of the trouble we have lately been having with the quantum-mechanical measurement problem (not the standard way, mind you, and certainly not the only way; but a way that nonethe-less be worth exploring) that suggests that there are fairly prosaic physical circumstances under which it might not be entirely beside the point to look around for observable violations...
We study the creation of polarisation entanglement by means of optical entanglement swapping (Zukowski et al., [Phys. Rev. Lett.71, 4287 (1993)]). We show that this protocol does not allow the creation of maximal ‘event-ready’ entanglement. Furthermore, we calculate the outgoing state of the swapping protocol and stress the fundamental physical difference between states in a Hilbert space...
The processes of radiation damping and decoherence in Quantum Electrodynamics are studied from an open system’s point of view. Employing functional techniques of field theory, the degrees of freedom of the radiation field are eliminated to obtain the influence phase functional which describes the reduced dynamics of the matter variables. The general theory is applied to the dynamics of a single electron...
It is well known that the dynamical mechanism of decoherence may cause apparent superselection rules, like that of molecular chirality. These ‘environment-induced’ or ‘soft’ superselection rules may be contrasted with ‘hard’ superselection rules, like that of electric charge, whose existence is usually rigorously demonstrated by means of certain symmetry principles. We address the question of whether...
Classical mechanics and standard Copenhagen quantum mechanics respect subspace implications. For example, if a particle is confined in a particular region R of space, then in these theories we can deduce that it is confined in regions containing R. However, subspace implications are generally violated by versions of quantum theory that assign probabilities to histories, such as the consistent histories...
The loss of coherence of a quantum system coupled to a heat bath as expressed by the reduced density matrix is shown to lead to the mis-characterization of some systems as being incoherent when they are not. The spin boson problem and the harmonic oscillator with massive scalar field heat baths are given as examples of reduced incoherent density matrices which nevertheless still represent perfectly...
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