论文标题
驱动腔量系统中的量子频率锁定和下转换
Quantum frequency locking and down-conversion in a driven cavity-qubit system
论文作者
论文摘要
我们研究了一个定期驱动的Qubit，耦合到量化的腔模式。尽管它显然很简单，但该系统仍支持各种外来现象，例如[Martin等人，PRX 7，041008（2017）]最近发现的拓扑频率转换。在这里，我们报告了在该平台中发生的一种质性不同的现象，在该平台中，腔模式的振荡将其频率锁定为驱动频率$ω$的理性分数$ r/q $。我们称量子频率锁定的这种现象的特征是出现了$ q $ tuplets nastary（floquet）状态的固定剂，其准固态被$ω/q $隔开，直到指数为小校正。这些状态的Wigner函数几乎是相同的，并且在相空间中表现出高度规则和对称的结构。与Floquet时间晶体类似，这些状态是模型中离散的时间翻译对称性破坏的基础。我们开发了一种分析和预测模型中量子频率锁定的半经典方法，并使用它来识别其发生的条件。
We study a periodically driven qubit coupled to a quantized cavity mode. Despite its apparent simplicity, this system supports a rich variety of exotic phenomena, such as topological frequency conversion as recently discovered in [Martin et al, PRX 7, 041008 (2017)]. Here we report on a qualitatively different phenomenon that occurs in this platform, where the cavity mode's oscillations lock their frequency to a rational fraction $r/q$ of the driving frequency $Ω$. This phenomenon, which we term quantum frequency locking, is characterized by the emergence of $q$-tuplets of stationary (Floquet) states whose quasienergies are separated by $Ω/q$, up to exponentially small corrections. The Wigner functions of these states are nearly identical, and exhibit highly-regular and symmetric structure in phase space. Similarly to Floquet time crystals, these states underlie discrete time-translation symmetry breaking in the model. We develop a semiclassical approach for analyzing and predicting quantum frequency locking in the model, and use it to identify the conditions under which it occurs.
