论文标题
使用量子Szilard发动机的两级系统超极化
Two-level system hyperpolarization using a quantum Szilard engine
论文作者
论文摘要
固态物理学的先天复杂性使超导量子电路与不受控制的自由度相互作用，从而降低了它们的连贯性。通过使用简单的稳定序列，我们表明，超导磁通量量子量子与未知来源的两级系统（TLS）环境耦合，相对较长的能量放松时间超过$ 50 \，\ \ text {ms {ms} $。用主动反馈控制回路实施量子Szilard发动机，使我们能够确定量子加热还是冷却其TLS环境。可以将TLSS冷却，从而导致量子群降低四倍，或者可以将其加热以表现为对应于$ \ sim 80 \，\％$的Qubit种群的负温度环境。我们表明，TLSS和量子位是彼此的主要损失机制，并且量子放松与TLS种群无关。因此，理解和缓解TLS环境不仅对于改善量子寿命至关重要，而且对于避免非马克维亚Qubit动态。
The innate complexity of solid state physics exposes superconducting quantum circuits to interactions with uncontrolled degrees of freedom degrading their coherence. By using a simple stabilization sequence we show that a superconducting fluxonium qubit is coupled to a two-level system (TLS) environment of unknown origin, with a relatively long energy relaxation time exceeding $50\,\text{ms}$. Implementing a quantum Szilard engine with an active feedback control loop allows us to decide whether the qubit heats or cools its TLS environment. The TLSs can be cooled down resulting in a four times lower qubit population, or they can be heated to manifest themselves as a negative temperature environment corresponding to a qubit population of $\sim 80\,\%$. We show that the TLSs and the qubit are each other's dominant loss mechanism and that the qubit relaxation is independent of the TLS populations. Understanding and mitigating TLS environments is therefore not only crucial to improve qubit lifetimes but also to avoid non-Markovian qubit dynamics.
