Sensitivity Enhancement of NV-based Ramsey Spectroscopy

Improving the sensitivity and contrast remains crucial in the Ramsey measurement techniques based on Nitrogen vacancy (NV) centers in diamond. In this work, we investigate the phase-shift sensitivity to the pulse amplitude in Ramsey spectroscopy. We show that in the presence of an AC-Zeeman shift due to additional quantum states, the phase shift of the Ramsey-fringes is insensitive to variations in pulse amplitude, for properly chosen values of the one-photon detuning. Additionally, we present a method for improving the sensitivity using the fractional stimulated Raman adiabatic passage (F-STIRAP) technique. F-STIRAP, which creates a maximally coherent superposition in an adiabatic and robust manner, followed by a free evolution and a time-reversed F-STIRAP allows the measurement of the double quantum (DQ) frequency in the nuclear spin triplet of an NV center. The insensitivity to amplitude fluctuations and enhanced measurement contrast of this scheme promises significant improvements in the NV-based rotation sensors.