Microwave Remote\nSensing with Hybrid Quantum Receiver

Detecting a microwave signal that\nis emitted or reflected\nby distant\ntargets is a powerful tool in fundamental science and industrial technology.\nSolid-state spins provide an opportunity to realize quantum-enhanced\nremote sensing under ambient conditions. However, the weak interaction\nbetween the free-space signal and atomic size sensor limits the sensitivity.\nThis hinders the realization of practical quantum remote sensing.\nHere, we demonstrate active microwave remote sensing with a diamond-based\nhybrid quantum receiver by combining electromagnetic field localization\nat nanoscale with quantum spin manipulation. A method of differential\nspin refocusing (DSR) is developed to overcome the challenge of reducing\nthe impact of inhomogeneities in spin–signal interaction, while\nthe strength of interaction is enhanced by more than 3 orders with\nnanostructure. It improves the coherent interaction time of quantum\nreceiver by 30-fold, substantially enhancing the sensitivity and stability.\nBy detecting the reflected microwave with picotesla sensitivity, diamond\nremote sensing monitors the real-time status of a centimeter-sized\ntarget at 2 m distance. Our method is general to various solid-state\nspins. The results will expand the applications of solid-state spin\nquantum sensors in areas ranging from medical imaging to resource\nsurvey.