磁通泵浦SQUID谐振器中基于占据态选择的光子对相互作用
Occupation-selective photon-pair interactions in a flux-pumped SQUID resonator
- Universidade Estadual de Ponta Grossa（蓬塔格罗萨州立大学）
- Universidade Estadual Paulista (UNESP)（圣保罗州立大学）
- Hainan Bielefeld University of Applied Sciences（海南比勒费尔德应用科学大学）
机构由 AI 辅助整理，请以论文原文为准。
中文总结 AI 辅助
该研究在磁通泵浦SQUID谐振器中识别出占据态条件化的光子对相互作用，控制器模通过对角和非线性约瑟夫森效应分别调控对共振频率与跃迁强度，实现玻色子Fock格中的选择性跃迁及纠缠与非高斯态产生。
中文摘要 AI 辅助
磁通泵浦约瑟夫森电路为参量光子产生和多模玻色子控制提供了通用平台。我们识别出一种当两个谐波简正模参与同一驱动SQUID坐标时出现的占据态条件化对相互作用。我们考虑一个简并对过程，其中在信号模中产生或湮灭两个光子，而第二个谐波模的占据态保持不变。尽管该控制器模不交换激发，它同时修改了对共振频率和对跃迁强度。这两种效应具有不同的物理起源：对角约瑟夫森非线性移动了对共振，而非线性约瑟夫森矩阵元使避免交叉间隙本身依赖于控制器占据态。从完整的约瑟夫森余弦出发，我们发展了互补的时间相关薛定谔-沃尔夫和马格努斯描述，揭示了负责该相互作用的直接和虚过程，并将所得有效理论与未展开双模电路哈密顿量的数值收敛Floquet处理进行了基准比较。占据态依赖性产生二维对谱，使得能够在玻色子Fock晶格内实现选择性跃迁。当控制器制备在相干叠加态时，同一相互作用将该条件动力学转换为信号-控制器纠缠和控制器依赖的非高斯态产生。可观测级比较进一步表明，对跃迁强度的变化不能仅由占据态依赖的共振移动来复现。这些结果建立了一种玻色子控制的参量相互作用，其中一个谐波模的状态控制另一个模中非线性过程的谱位置和耦合强度。
英文摘要
Flux-pumped Josephson circuits provide a versatile platform for parametric photon generation and multimode bosonic control. We identify an occupation-conditioned pair interaction that arises when two harmonic normal modes participate in the same driven SQUID coordinate. We consider a degenerate pair process in which two photons are created or annihilated in a signal mode while the occupation of a second harmonic mode remains unchanged. Although it does not exchange excitations, this controller mode modifies both the resonance frequency and the strength of the pair transition. The two effects have different physical origins: diagonal Josephson nonlinearities shift the pair resonance, whereas the nonlinear Josephson matrix element makes the avoided-crossing gap itself depend on the controller occupation. Starting from the full Josephson cosine, we develop complementary time-dependent Schrieffer--Wolff and Magnus descriptions that expose the direct and virtual processes responsible for this interaction, and benchmark the resulting effective theory against a numerically converged Floquet treatment of the unexpanded two-mode circuit Hamiltonian. The occupation dependence produces a two-dimensional pair spectrum that enables selective transitions within the bosonic Fock lattice. When the controller is prepared in a coherent superposition, the same interaction converts this conditional dynamics into signal--controller entanglement and controller-dependent non-Gaussian state generation. Observable-level comparisons further show that the variation of the pair-transition strength cannot be reproduced by occupation-dependent resonance shifts alone. These results establish a boson-controlled parametric interaction in which the state of one harmonic mode controls both the spectral position and the coupling strength of a nonlinear process in another.
