Diamond Quantum Magnetic Sensor toward a Precision Comparison of Currents with a Current Comparator

In this paper, a diamond nitrogen-vacancy (NV) magnetic sensor toward a precision comparison of currents with a current comparator is described. A diamond quantum sensor can sensitively detect magnetic fields based on the Zeeman effect of the electron spin state of NV centers, which may be used as a detector in a current comparator. The compact diamond quantum sensor head has been developed, being capable of positioning in an air gap formed in a ring-shaped magnetic core. The sensor exhibited the DC magnetic noise floor of less than $100\,{\text{pT}}/\sqrt {{\text{Hz}}} $. The obtained magnetic noise floor is less than equivalent current noise level required for a current comparator.