Dephasing and relaxational polarized sub-Ohmic baths acting on a two-level system

Abstract

We study a quantum two-level system under the influence of two independent baths, i.e., a sub-Ohmic pure dephasing bath and an Ohmic or sub-Ohmic relaxational bath. We show that cooling such a system invariably polarizes one of the two baths. A polarized relaxational bath creates an effective asymmetry. This asymmetry can be suppressed by additional dephasing noise. This being less effective, the more dominant low frequencies are in the dephasing noise. A polarized dephasing bath generates a large shift in the coherent oscillation frequency of the two-level system. This frequency shift is little affected by additional relaxational noise nor by the frequency distribution of the dephasing noise itself. As our model reflects a typical situation for superconducting phase qubits, our findings can help optimize cooling protocols for future quantum electronic devices.

Quantum Thermal Transport Beyond Second Order with the Reaction Coordinate Mapping

“…The spin-boson model has been recently extended to explore dynamics and transport effects using a general coupling operator with both diagonal and off-diagonal couplings 18,[49][50][51][52][53][54][55][56][57][58][59] . For heat transport, the coupling operators to the different reservoirs do not commute.…”