发表机构
Aalto University School of Science; University of Chicago（阿尔托大学理学院; 芝加哥大学）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
本研究分析孤立耦合量子比特系统中，弱耦合主方程下退相干与热化现象，发现非线性三波混频可确保长时间极限下达到由初始能量唯一确定温度的热分布，并提出超导量子电路实验方案。
AI 中文摘要
一个幺正演化的系统，根据定义不会退相干或热化。然而，如果考虑幺正系统的一部分，情况则有所不同。在此，我们分析一组孤立的耦合量子比特，每次取一个量子比特作为子系统，并为其自洽地写出弱耦合主方程。弱非谐振子与理想量子比特（二能级系统）表现出退相干，即密度矩阵的对角元在长时间极限下达到稳态，而理想量子比特的非对角元则指数衰减。对于量子比特之间的线性耦合，仅简并的量子比特发生相互作用，系统不会达到热分布。然而，非线性——在我们的分析中以三波混频的形式出现——确保了长时间极限下的热分布，其中温度由初始非热态中的能量唯一确定。最后，我们提出一个基于超导量子电路的潜在实验方案。
英文摘要
A system evolving unitarily does not dephase or thermalize by definition. Yet, if one considers a part of a unitary system, situation is different. Here we analyze an isolated set of coupled qubits taking one qubit at a time as a subsystem, and writing self-consistently a weak-coupling master equation for it. Weakly anharmonic oscillators and ideal qubits (two-level systems) demonstrate dephasing, i.e. the diagonal elements of the density matrix reach a steady-state in the long-time limit, and the off-diagonal elements of ideal qubits decay exponentially. For the linear coupling between the qubits, only the degenerate ones interact, and the system does not reach thermal distribution. However, non-linearity, in our analysis in form of three-wave mixing, ensures a thermal distribution in the long time limit, where the temperature is determined uniquely by the energy in the initial non-thermal state. Finally, we present a potential experimental scheme based on a superconducting quantum circuit.
