Diamond based quantum sensing is a fast-emerging field with both scientific and technological importance. The nitrogen-vacancy (NV) center, a crystal defect in diamond, is a unique model system for microwave sensing application due to its excellent photo-stability, long spin coherence time in ambient conditions. In this work, we systematically optimized the measurement parameters for microwave sensing. The system noise is analyzed, and 1/f noise is suppressed by introducing a differential algorithm. The gain of avalanche photodiode and the gating window of the pulsed fluorescence is optimized to further suppress the noise floor. The decoherence of spin is characterized by varying the duration of the laser and microwave. The minimal detectable power on a standard microstrip is characterized with sampling time down to 1 ms, showing flat frequency dependence. The results have important implications toward fast measurement of broadband microwave power, especially in the field of IC testing and radar signal processing under intense electromagnetic interference.

Diamond based quantum sensing is a fast-emerging field with both scientific and technological significance. The nitrogen-vacancy (NV) center, a crystal defect in diamond, has become a unique object for microwave sensing applications due to its excellent stability, long spin coherence time and optical properties at ambient condition. In this work, we use diamond NV center as atomic receiver to demodulate On-Off Keying (OOK) signal transmitted in broad frequency range (2-14GHz in a portable benchtop setup). We proposed a unique algorithm of voltage discrimination and demonstrated audio signal transceiving with fidelity above 99%. This diamond receiver is attached to the end of a tapered fiber, having all optic nature, which will find important applications in data transmission tasks under extreme conditions such as strong electromagnetic interference, high temperatures and high corrosion.

With the increasing integration and complexity of chips, the problem of wafer‐level electromagnetic compatibility (EMC) is becoming more and more prominent, and the spatial resolution and operating frequency of existing EMC test techniques can no longer meet the demand for wafer‐level EMC testing. In this work, a surface H‐field imaging system based on a micron‐sized diamond crystal containing nitrogen‐vacancy centers is proposed, which is micrometer resolved, quantum calibrated, frequency tunable, and nonintrusive to the H‐field of the device to be tested. The surface H‐field of a limiter chip at different input power is scanned for imaging, revealing how the energy is dissipated across the chip when exceeding limiting power. The result is essential for understanding the workings of the limiter chip and for optimizing the chip design.

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