Palm T, Nalbach P
Fachbereich Wirtschaft & Informationstechnik, Westfälische Hochschule, Münsterstrasse 265, 46997 Bocholt, Germany.
J Chem Phys. 2019 Jun 21;150(23):234108. doi: 10.1063/1.5098467.
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.
我们研究了一个受两个独立热库影响的量子二能级系统，即一个亚欧姆纯退相干热库和一个欧姆或亚欧姆弛豫热库。我们表明，冷却这样一个系统总会使两个热库中的一个发生极化。极化的弛豫热库会产生有效的不对称性。这种不对称性可以通过额外的退相干噪声来抑制。退相干噪声中低频成分越占主导，这种抑制效果就越差。极化的退相干热库会使二能级系统的相干振荡频率产生较大偏移。这种频率偏移几乎不受额外的弛豫噪声影响，也不受退相干噪声本身的频率分布影响。由于我们的模型反映了超导相位量子比特的典型情况，我们的研究结果有助于优化未来量子电子器件的冷却方案。
