Open quantum system

This chapter has provided an introduction to the ideas underlying the quantum theory of atoms in molecules, the theory that gives theoretical expression to chemical concepts and enables one to employ these concepts in a quantitative manner for prediction and for understanding of chemical problems. The theory is particularly well-suited to problems in medicinal chemistry where the important role of building block molecules enables one to make maximum use of the transferability of atoms and groups defined as open quantum systems. 

A promising simplification has been proposed by Bader (1990) who has shown that the electron density in a molecule can be uniquely partitioned into atomic fragments that behave as open quantum systems. Using a topological analysis of the electron density, he has been able to trace the paths of chemical bonds. This approach has recently been applied to the electron density in inorganic crystals by Pendas et al. (1997, 1998) and Luana et al. (1997). While this analysis holds great promise, the bond paths of the electron density in inorganic solids are not the same as the more traditional chemical bonds and, for reasons discussed in Section 14.8, the electron density model is difficult to compare with the traditional chemical bond models. 

The underlying issue is broader Coherent control was originally conceived for closed systems, and it is a priori unclear to what extent it is applicable to open quantum systems, that is, systems embedded in their ubiquitous environment and subject to omnipresent decoherence effects. These may have different physical origins, such as the coupling of the system to an external environment (bath), noise in the classical fields controlling the system, or population leakage out of a relevant system subspace. Their consequence is always a deviation of the quantum-state evolution (error) with respect to the unitary evolution expected... 

FROM COHERENT TO INCOHERENT DYNAMICAL CONTROL OF OPEN QUANTUM SYSTEMS 139... 

H.-P. Breuer and F. Petruccione. The Theory of Open Quantum Systems. Oxford University Press, Oxford (2002). 

I. Burghardt and H. Tamura, in Dynamics of Open Quantum Systems, ed. K. H. Hughes (CCP6, Daresbury, 2006). 

Abstract. The dynamics in open quantum systems is often described by quantum... 

Open quantum systems have attracted much attention over the last decades. While most of the studies dealt with systems coupled to bosonic heat baths, recently systems coupled to fermionic reservoirs describing for example molecular wires have been in the focus of many investigations. This chapter will not try to give a concise overview of the available literature but will focus on a particular approach time-local (TL) quantum master equations (QMEs) and in particular their combination with specific forms of the spectral density. 

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