Investigating Microwave Raman Transitions Beyond the Rotating Wave Approximation in the Electronic Ground State of the Nitrogen-Vacancy Center

Up to now, spin manipulation experiments with the NV center were mostly limited to applying subsequent monochromatic microwave pulses, manipulating only single electronic transitions at a time. In our work we explore the possibility of applying multitone microwave pulses, allowing a full simultaneous control of all three electronic ground states of the NV center. This here presented spin manipulation scheme opens up new measurement possibilities, which could be used to increase the NV center’s magnetic field sensitivity.
We will present the implementation of a spin-forbidden coherent population swapping between the m_s = -1 and m_s = +1 states, without undergoing the spin allowed transition into the m_s = 0 state via microwave Raman transitions and compare our experimental results with theoretical calculations. These Raman transitions are operated in a regime exceeding the rotating wave approximation (RWA). This has hardly been investigated as the RWA is traditionally applied in the single atom community. Due to the short coherence times, a low detuning has to be chosen, which in turn causes fast Raman transitions and a breakdown of the RWA. An indication for this is an experimentally observed beating signal which we want to utilize for faster and more robust population swapping.