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Published online 30 April 2008 | 453, 22-25 (2008) | doi:10.1038/453022a
News Feature
Physics: Quantum all the way
How does our classical world emerge from the counterintuitive principles of quantum theory? Can we even be sure that the world doesn't 'go quantum' when no one is watching? Philip Ball talks to the theorists and experimentalists trying to find out.
Keith Schwab builds bridges. By most people's standards, they are very small bridges indeed: around 8 thousandths of a millimetre long and 200 millionths of a millimetre wide, visible only under a microscope.
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This is something quite extraordinary – a decoherence theory that attempts to link the illusive quantum realm to the realistic classical realm. Quantum theory bends on AND/OR, a thing can be both AND as well as OR simultaneously, whereas classical theory suggests otherwise. Quantum phenomena continue to split physicists into camps. The 'Tao' of Physics would continue to exert its presence. In the final analysis, the thing that can be described is not Tao, the thing that can be named cannot be Tao too. Perhaps the mystic Lao-Tzu has been right all this time. (Tan Boon Tee)
Decoherence by itself cannot explain the quantum-classical transition; it must be supplemented by the many-worlds interpretation. This is because while decoherence destroys interference amongst alternatives, it preserves superpositions, since it works within the framework of linear quantum mechanics. An alternate explanation for emergent classicality, not ruled out by experiments, is that quantum mechanics is modified, say to a non-linear theory, on mesoscopic scales. As a result of the non-linearity, the life-time of a quantum superposition becomes dependent on the number of degrees of freedom of the system, and goes to zero for large systems. Experiments should be attempted, to test for the presence/absence of non-linearity in quantum mechanics on the mesoscopic scale. T. P. Singh, Tata Institute of Fundamental Research, Mumbai
Very good review of Philip Ball of the 'hottest potato' in quantum physics. That's clear that decoherence is the main obstacle on the way to macroscopic entanglement. So, does it mean that this phenomena is possible only at ultra low temperature at conditions of macroscopic Bose condensation, like superfluidity or superconductivity? I have developed the physical model, describing possible mechanism, turning the mesoscopic Bose condensation (coherent molecular clusters) to macroscopic one, via intermediate stage of IR photons exchange between these remote in water coherent clusters. The nonuniform macroscopic Bose condensation (BC) can be a result of remote EM interaction and entanglement between cluster in state of mesoscopic Bose condensate (i.e. coherent water clusters inside the microtubules of neurons). This system of nonuniform macroscopic BC is coherently 'flickering' with frequency 10^6 - 10^7 per second of simulateneous disassembly - assembly of huge number of water clusters inside the same microtubule and remote microtubules also. This mechanism is described in chapter "Cycle of Mind" of my recent book: “The Hierarchic Theory of Liquids and Solids. Computerized Applications for Ice, Water, and Biosystems†(2008), just published by Nova Science Publ. (NY, USA). This book is also available online: http://arxiv.org/abs/physics/0102086 . This theory proves new basic idea of coherent water clusters, as mesoscopic Bose condensate, since they are located in the volume of 3D de Broglie standing waves, related to molecular librations. Using Hierarchic theory based computer program, I can calculate over 300 physical parameters of water, including number of molecules in clusters and their life-time in wide T-range. The results of evaluation of dimensions of water clusters in ice and water are presented in my book: http://arxiv.org/ftp/physics/papers/0102/0102086.pdf in section 6.3.4, see Figs. 6 and 7. I hope that this new approach to condensed matter problems will be also useful in understanding of macroscopic entanglement and nonlocality phenomena, which looks to be much more general phenomena, than it is accepted. Alex Kaivarainen alex@h-systems.be http://web.petrsu.ru/~alexk
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According to some theories the thermo-quantum dynamics of an open system obeys a nonlinear Schrodinger equation (arXiv:0711.1442). The linear Schrodinger equation is applicable only to closed systems but they are not present in the Nature due to the infinite range of the fundamental interactions (the only exception is probably the whole Universe). Therefore, the linear Schrodinger equation is an approximation and this questions the accuracy of many effects due to the superposition principle following from to its linearity. Thus, the Fourier transform and Wigner function are no more applicable, while the Bohmian mechanics seems more plausible (arXiv:0803.4409). Another example is the traditional theory of decoherence, which is based on a linear master equation and hence the decoherence takes place continuously in time. According to the new theory, the entropy (information) exchange between the system and its environment results in a nonlinear Schrodinger equation. Therefore, from the very beginning decoherence takes place, thus solving the contradiction between quantum and classical reality immediately. For instance, in the Schrodinger cat paradox the entropy of mixing causes non-linear terms in the Schrodinger equation and hence the outcome is either alive or dead cat but never a linear superposition of these excluding events.