Controlling the nuclear spin of NV centers in random orientations toward memory-enhanced quantum sensing*

In medicine and industry, there is a high demand for measuring magnetic field vectors with high spatial resolution and sensitivity under ambient conditions. Due to limited spatial resolution and particular working temperatures, existing magnetic sensors such as SQUID are only sometimes available. One of the promising candidate platforms for such high-performance magnetometers is the nitrogen-vacancy (NV) center, hosting an electronic spin accompanied by a ¹⁴N nuclear spin in diamond. The efficient method to improve the signal-to-noise ratio is to use a nitrogen nuclear spin as a memory. However, controlling the nuclear spin has been demonstrated only in the case of the static magnetic field along the NV axis. Here, we present our novel idea of polarizing the nuclear spin and suppressing the modulation under a static magnetic field with an arbitrary orientation. Our approach may pave the way toward enhanced sensitivity of vector magnetometry by NV center.