Diamond NV center quantum magnetic sensor using a dual-frequency broadband antenna

This paper presents a compact broadband antenna that overcomes bandwidth limitations in a diamond nitrogen-vacancy (NV) center-based quantum magnetic sensor. Conventional antennas struggle to achieve both broadband operation and compact integration, restricting the sensitivity and dynamic range of the sensor. The broadband antenna based on a dual-frequency monopole structure achieves a bandwidth extension of 777 MHz at the Zeeman splitting frequency of 2.87 GHz, with the dual resonant points positioned near 2.87 GHz. Additionally, high-resolution imaging of the microwave magnetic field on the antenna surface was performed using a diamond optical fiber probe, which verified the dual-frequency design principle. Experimental results using the proposed antenna demonstrate the outstanding performance of the NV center-based magnetic sensor: a sensitivity of 55 nT/Hz^1/2 and a dynamic range of up to 54.0 dB. Compared to sensors using conventional antennas, the performance has been significantly improved.