Figure 4. Raman-based population transfer between ground states.

(a) Spectrum displaying spectral position of the SiV⁻, as well as width and detuning of the CW Pump/Readout and pulsed Raman rotation laser involved. (b) Schematic pulse sequence and measured fluorescence response for the Raman beam switched off as well as P_Raman=4 μW (red). (c) Transferred population in upper ground state as a function of the average power in the Raman beam. (d) Ramsey interference generated by two subsequent Raman pulses verifying coherent transfer. Solid lines show simulations using the four-level density matrix model with the relative driving strength of both Raman transitions as the only free parameter. The model indicates that the ratio of the driving strengths of transitions C and D in the Raman beam is about 1:0.7 after optimizing the polarization.