Quantum sensing for electric current based on NMOR atomic magnetometer

Based on the principle of electromagnetic mutual inductance, contactless and high-precision current measurement is essential for a wide range of applications. However, conventional current sensors suffer from inherent limitations in sensitivity and precision, hindering further performance enhancement, especially for weak current. This work proposes a novel approach for current measurement utilizing a nonlinear magneto-optical rotation (NMOR) atomic magnetometer, which is a quantum sensor designed to detect the magnetic field generated by current. A contactless current measurement system with a wide range from the nanoampere (nA) level up to 800 mA is designed. The significant advantages of the NMOR atomic magnetometer for current sensing are thoroughly analyzed both theoretically and experimentally. For lower current range (≤ 1 mA), the system achieves a noise spectrum of 250 pA/Hz^1/2 across 20–900 Hz frequency band. For higher current (mA level), the system demonstrates exceptional precision with an average standard deviation of 1.06 ppm in the experiment. Furthermore, utilizing the high sensitivity of the NMOR atomic magnetometer, the noise characteristics of the current source are evaluated. This work offers valuable insights for current metrology and the development of portable current reference devices.