Magnetic field sensing enhancement via triple tone excitation of nitrogen-vacancy center *

Nitrogen-vacancy (NV) centers are powerful magnetic field sensors at room temperature, heralded for their high sensitivity and ease of manipulation, reaching sensitivities sub pT/√Hz [1, 2].

Being vectorial defects in a static diamond matrix, carefully placing a magnet nearby lets us query each possible orientation, even when using ensembles. This coupling to the magnetic field is modified by the spin of the nearby nitrogen, introducing the hyperfine splitting.

Using the quantum demonstrator from SBQuantum (Sherbrooke, Canada) and the solution from Keysight Technologies, we demonstrate that by a mixture of three microwaves pulses that target each of the transitions generated by the hyperfine coupling to the nearby nitrogen, we obtain a straightforward improvement in contrast and therefore an increase in sensitivity. Although there is still room for improvement, combining this method with an experimental re-design of the pulse sequence allowed us to reduce the linewidth, increasing the sensitivity once again. These promising results will help bolster other pulsed experiments to increase the sensitivity further.



[1] T. Wolf et al., Phys. Rev. X5, 041001 (2015).

[2] C. Zhang et al, Phys. Rev. Appl.15, 064075 (2021).



*This work was supported in part by the National Research Council of Canada Quantum Sensors Challenge Program