时延波导量子电动力学中的涌现非马尔可夫性
Emergent non-Markovianity in time-delayed waveguide QED
AI总结：
本文研究时延波导量子电动力学装置，发现即使延迟时间很小，增加发射器产生的集体效应可涌现非马尔可夫性，其影响依赖于状态，结果为量子多体系统马尔可夫近似及量子设备规模化提供了参考。
AI中文摘要：
量子系统总是与周围环境耦合，简化该问题的常用理论方法是在马尔可夫近似下对环境求迹，该近似假设环境在系统演化的时间尺度上无记忆。在相互作用的多体系统中，提取多个集体时间尺度中哪些是相关的往往并非易事。我们考虑具有单个激发的时延波导量子电动力学（waveguide QED）装置，通过固定最大传播时间并增加发射器数量，证明即使延迟时间很小，集体效应也足以引发非马尔可夫性。记忆的影响本质上依赖于状态：对于超辐射态，相关系统时间尺度为超辐射寿命，相关库时间尺度为端到端延迟时间；对于亚辐射态，两个时间尺度均依赖于特定状态的结构。我们的结果表明，在量子多体系统中谨慎进行马尔可夫近似的重要性，并强调了在将量子设备扩展到大系统规模时需避免的潜在陷阱。
英文摘要：
Quantum systems are invariably coupled to a surrounding environment. A common theoretical method to simplify the problem is to trace over the environment under a Markov approximation, which assumes that the environment holds no memory over the timescales that the system evolves under. In interacting many-body systems, it is often not trivial to extract which of the multiple collective timescales are relevant. We consider a time-delayed waveguide QED setup with a single excitation. By fixing the maximum propagation time and increasing the number of emitters, we show that, even for small delay times, collective effects are sufficient to cause non-Markovianity. The impact of memory is intrinsically state-dependent. For superradiant states, the relevant system timescale is the superradiant lifetime while the relevant bath timescale is the end-to-end delay time. For subradiant states, both timescales depend on the structure of the specific state. Our results demonstrate the importance of prudently making Markov approximations in quantum many-body systems, and highlight potential pitfalls to avoid in scaling up quantum devices to large system sizes.
