The innate complexity of solid-state physics exposes superconducting quantum circuits to interactions with uncontrolled degrees of freedom degrading their coherence. By implementing a quantum Szilard engine with an active feedback control loop, we show that a superconducting fluxonium qubit is coupled to a two-level system (TLS) environment of unknown origin, with a relatively long intrinsic energy relaxation time exceeding 50 ms. 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 ~80%. We show that the TLSs and qubit are the dominant loss mechanism for each other and that qubit relaxation is independent of the TLS populations. Understanding and mitigating TLS environments is, therefore, not only crucial to improve the qubit lifetimes but also to avoid non-Markovian qubit dynamics.

固态物理学的先天复杂性使超导量子电路暴露于与不受控制的自由度相互作用，从而降低了它们的相干性。通过实施具有主动反馈控制回路的量子 Szilard 引擎，我们表明超导镨量量子位耦合到来源不明的两能级系统 (TLS) 环境，具有超过 50 毫秒的相对较长的固有能量弛豫时间。TLS 可以冷却，导致量子比特数量减少四倍，或者它们可以被加热以表现为负温度环境，对应于约 80% 的量子比特数量。我们表明 TLS 和量子比特是彼此的主要损失机制，并且量子比特松弛独立于 TLS 种群。因此，理解和缓解 TLS 环境是