AI 中文总结
本研究通过双音驱动约瑟夫森结克尔振荡器实现少光子简并参量共振，证实三音量子描述可准确复现实验可观测量，为参量放大器及量子-经典交叉研究提供新途径。
AI 中文摘要
多音外部驱动为无需直接调制器件的参量物理研究提供了途径，但少光子区域内参量响应的有效性仍未得到充分探索。本研究将两个相干微波音施加到约瑟夫森结克尔振荡器上，通过四波混频激发简并参量下转换。利用透射光谱，观察到该响应保留了定性的半经典克尔参量振荡器结构，包括其不稳定叶和双稳态相空间拓扑。值得注意的是，研究表明传统的单模简化无法定量描述该系统：当单光子克尔位移K超过腔线宽κ时，预测的交流斯塔克位移被严重低估，且相关分布可能并非完全物理的。相反，研究表明完整的三音量子描述能准确复现实验可观测量。在此，驱动音的量子涨落在动力学上主导了耗散，所有三个相互作用音均处于深少光子极限，其中预期的半经典宏观叶因与量子方差的强烈混合而发生基本重整化。本研究结果确立了双音驱动克尔振荡器作为潜在参量放大器的地位，并为驱动耗散电路中量子-经典 crossover（ crossover 译为“交叉”）的探索开辟了新视野。
英文摘要
Multi-tone external driving offers a route to parametric physics without directly modulating the device. However, the validity of the parametric response in the few-photon regime remains underexplored. Here, we apply two coherent microwave tones to a Josephson-junction Kerr oscillator and stimulate degenerate parametric downconversion via four-wave mixing. Using transmission spectroscopy, we observe that the response retains the qualitative semiclassical Kerr parametric oscillator structure, including its instability lobe and bistable phase-space topology. Interestingly, we demonstrate that a conventional single-mode reduction fails to capture the system quantitatively: the predicted AC Stark shift is severely underestimated, and the reported distributions might not be fully physical when the single-photon Kerr shift $K$ exceeds the cavity linewidth $κ$. Instead, we show that a full three-tone quantum description accurately reproduces the experimental observables. There, quantum fluctuations of the drive tones become dynamically dominant over dissipation, and all three interacting tones operate in a deep few-photon limit where the expected semiclassical macroscopic lobes undergo fundamental renormalization due to profound mixing with quantum variance. Our results establish two-tone-driven Kerr oscillators as potential parametric amplifiers and open new horizons to explore the quantum-to-classical crossover in driven-dissipative circuits.
