Radiofrequency Receiver Based on Isotropic Solid-State Spins

Optically addressable solid-state spins have been proposed as robust radiofrequency (RF)–optical transducers sensitive to a specific RF frequency tuned by external magnetic fields but often require precise field alignment with the system’s symmetry axis. Here we introduce an isotropic solid-state spin system, namely, weakly coupled spin pairs in hexagonal boron nitride, which acts as an RF–optical transducer independent of the direction of the tuning magnetic field. Using this platform, we demonstrate a single-frequency RF receiver with frequency tunability from 0.1 to 19 GHz and an instantaneous wideband RF spectrum analyzer by applying a magnetic field gradient to encode RF frequency into spatial position. We utilize the spectrum analyzer to detect free-space-transmitted RF signals matching the strength and frequency of typical Wi-Fi signals. This work exemplifies the unique capabilities of isotropic spins to operate as RF sensors, while circumventing the challenging requirement of precisely aligned magnetic fields facing conventional solid-state spins.