An Off-Resonant Quantum Collision Model: Realizing a Qubit Coupled with an Effective Negative-Temperature Bath

The quantum collision model provides a promising tool for investigating system-bath dynamics. Most studies of quantum collision models, however, are in the resonant regime. In quantum dynamics, the off-resonant interactions often result in exciting effects. Therefore, it is important to investigate the quantum collision models in the off-resonant regime. A bath with a negative absolute temperature is expected to be instrumental in the development of thermal devices. The design of an effective bath with negative absolute temperature coupled to a qubit is a significant component for developing such thermal devices. In this study, we establish an effective negative-absolute-temperature bath coupled to a qubit with a quantum collision model in the far-off-resonant regime. We conduct a detailed systematic investigation of the off-resonant collision model and determine the presence of an additional constraint on the collision duration resulting from the far-off resonant collision. The dynamics of the collision model in the far-off-resonant regime are different from those beyond the far-off-resonant regime. Numerical simulations are used to confirm the validity of the proposed approach.