ABSTRACT
This chapter describes the analysis of the effect of dissipation on quantum properties of double-well systems. The simple qualitative observation suggests that interaction with a dissipative bath can significantly alter physical properties of a quantum mechanical particle in a double-well potential. The chapter provides the description of real-time dynamics of the double-well systems in the presence of linear Ohmic dissipation. It shows that dissipation yields total loss of coherence and, hence, real-time dynamics of the system remains incoherent at all times. Drastic simplifications occur if one assumes that the average time the system remains in a state described by the diagonal density matrix strongly exceeds the time it spends in the off-diagonal state. The collective charge variable is canonically conjugate to that of the phase, thus also describing quantum states of a macroscopically large number of electron degrees of freedom.
