Quantum phenomena controls

In the concluding remark of Section 5.2 we asked the question whether the transition from confined chaos to global chaos K = Kc can be seen in an experiment with diatomic molecules. The technical feasibility of such an experiment is discussed in Section 5.4. Here we ask the more modest question whether, and if so, how, the transition to global chaos manifests itself within the framework of the quantum kicked rotor. Since the transition to global chaos is primarily a classical phenomenon, we expect that we have the best chance of seeing any manifestation of this transition in the quantum kicked rotor the more classical we prepare its initial state and control parameters. Thus, we choose a small value... 

The uncontrollable interaction of an open quantum system with its environment leads to complete loss of the information initially stored in its quantum state. This phenomenon is commonly referred to as decoherence, loss of coherence, or loss of fidelity. The question of how it is possible to avoid the negative influence of this process is one of the most interesting issues in modem quantum mechanics, and concerns many different fields of physics, in particular the domains of coherent control [Shapiro 2003] and quantum information processing [Cirac 1995 Mplmer 1999 Sackett2000],... 

Delaney [13] describes the solubilization mechanism as controlled by a double phenomenon the affinity of the compound for itself and the affinity of the compound for the solvent. The latter effect is simply described either by the log P property or by very sophisticated methods such as statistical thermodynamic or quantum mechanical techniques. These very intensive calculation methods have not yet proved their superiority over the simpler and faster methods that tend to mimic the successful log P fragment calculator. 

This novel effect has been termed non-Faradaic electrochemical modification of catalytic activity (NEMCA effect [5-15]) or electrochemical promotion [16] or in situ controlled promotion [20]. Its importance in catalysis and electrochemistry has been discussed by Haber [18], Pritchard [16] and Bockris [17], respectively. In addition to the group which first reported this new phenomenon [5-7], the groups of Lambert [12], Haller [10], Sobyanin [8], Comninellis [13], Pacchioni [21] and Stoukides [11] have also made important contributions in this area, which has been reviewed recently [14,15]. In this review the main phenomenological features of NEMCA for oxidation reactions are briefly surveyed and the origin of the effect is discussed in the light of recent kinetic, surface spectroscopic and quantum mechanical investigations. 

Decoherence in condensed phase typically slows down chemical reactions as has been exemplified by the non-radiative relaxation of solvated electrons [3,18,67]. In the case of an electron in water the difference in the rates of quantum decoherence induced in the electron subsystem by water and deuterated water explains the absence of a solvent isotope effect on the relaxation rate [18,67]. In rare instances, decoherence can enhance chemical reactivity. The SMF approach has been used to provide evidence for acceleration of a chemical reaction in a condensed phase due to the quantum anti-Zeno effect [55]. The mechanism indicates that the anti-Zeno effect involves both delocalization of the quantum dynamics and a feedback loop by coupling to the solvent. Believed to be the first example of the quantum anti-Zeno effect in chemistry, the observed phenomenon suggests the possibility of quantum control of chemical reactivity by choice of solvent. 

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