abstract
- © 2020, The Editor(s) (if applicable) and The Author(s), under exclusive license to Springer Nature Switzerland AG.The reduced density operator of a single qubit coupled to a quantum oscillator is time-periodic even for stationary Hamiltonians. We construct some quantum master equations for such density operator and show that they can be expressed in the Lindblad form. Although the qubit is treated as an open system that exchanges information with the oscillator (environment), the dynamics of the entire system is unitary and such that no information is lost at any time. The time-evolution of the qubit is therefore developed with balanced gain and loss profile. Some subtleties arise since the appropriate master equation must include not only the decay (diffusion) process but also the excitation of the qubit. The advances reported in this work are addressed to cover the decay process only.