Quantum sensors such as spin defects in diamond have achieved excellent performance by combining high sensitivity with spatial resolution. Unfortunately, these sensors can only detect signal fields with frequency in a few accessible ranges, typically low frequencies up to the experimentally achievable control field amplitudes and a narrow window around the sensors’ resonance frequency. Here, we develop and demonstrate a technique for sensing arbitrary-frequency signals by using the sensor qubit as a quantum frequency mixer, enabling a variety of sensing applications. The technique leverages nonlinear effects in periodically driven (Floquet) quantum systems to achieve quantum frequency mixing of the signal and an applied bias ac field. The frequency-mixed field can be detected using well-developed sensing techniques such as Rabi and CPMG with the only additional requirement of the bias field. We further show that the frequency mixing can distinguish vectorial components of an oscillating signal field, thus enabling arbitrary-frequency vector magnetometry. We experimentally demonstrate this protocol with nitrogen-vacancy centers in diamond to sense a 150-MHz signal field, proving the versatility of the quantum mixer sensing technique.

中文翻译：

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使用量子混频器感测任意频率场

金刚石中的自旋缺陷等量子传感器通过将高灵敏度与空间分辨率相结合，取得了优异的性能。不幸的是，这些传感器只能检测频率在几个可访问范围内的信号场，通常是低至实验上可实现的控制场幅度和传感器共振频率附近的窄窗口。在这里，我们开发并演示了一种通过将传感器量子比特用作量子混频器来感知任意频率信号的技术，从而实现各种传感应用。该技术利用周期性驱动 (Floquet) 量子系统中的非线性效应来实现信号的量子频率混合和施加的偏置交流场。可以使用成熟的传感技术（例如 Rabi 和 CPMG）检测频率混合场，而唯一的附加要求是偏置场。我们进一步表明，混频可以区分振荡信号场的矢量分量，从而实现任意频率的矢量磁力测量。我们用金刚石中的氮空位中心通过实验证明了该协议，以感测 150 MHz 信号场，证明了量子混频器传感技术的多功能性。