We propose a versatile scheme for multiphoton frequency up/down conversion in flux superconducting qubit circuits, driven by a pair of microwaves tuned near and far off the qubit resonance. Flux qubits can be engineered with strong anharmonicity such that the two lowest eigenstates are energetically well separated from the higher ones. We demonstrate the high order non-linear transitions between the two lowest levels in the three-photon regime, by coupling the qubit to bichromatic microwave fields with the same Rabi frequencies. Both up and down conversions are presented and accurately interpreted with many-mode Floquet formalism. An intuitive graph theoretic approach elucidates the physics of multiphoton pumping and population trapping. The analytical solutions also illustrate how controllability is achievable for desired single- or multiphoton pumping processes in a wide range of frequencies. The proposed design and theoretical approach are applicable in maintaining the inter-...

中文翻译：

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超导量子位电路中多光子泵浦的频率上/下转换

我们提出了一种通量超导量子位电路中多光子频率上/下转换的通用方案，该方案由一对调谐在接近或远离量子位共振的微波驱动。通量量子比特可以被设计成具有很强的非谐性，从而使两个最低的本征态在能量上与较高的本征态良好分离。通过将量子位耦合到具有相同拉比频率的双色微波场，我们证明了三光子域中两个最低能级之间的高阶非线性跃迁。上转换和下转换都可以通过多模式Floquet形式主义进行呈现和准确解释。直观的图论方法阐明了多光子泵浦和人口陷阱的物理原理。分析解决方案还说明了如何在很宽的频率范围内实现所需的单光子或多光子泵浦过程的可控性。所提出的设计和理论方法适用于维持相互之间的联系。