Fig. 3
From: Controlling the coherence of a diamond spin qubit through its strain environment
Spin coherence measurements. a SiV− level structure in the presence of strain and external magnetic field. A spin qubit is defined with levels \(\left| {1 \downarrow } \right\rangle\) and \(\left| {1 \uparrow } \right\rangle\) on the lower orbital branch of the GS. This qubit can be polarized, and prepared optically using the Λ-scheme provided by transitions C1 and C2. Phonon transitions within ground- and excited-state manifolds are also indicated. The upward phonon transition (phonon absorption process) can be suppressed at high strain, thereby mitigating the effect of phonons on the coherence of the spin qubit. b Coherent population trapping (CPT) spectra probing the spin transition at increasing values of the GS orbital splitting Δgs from top to bottom. Scale bar in bottom left represents a fluorescence signal contrast of 10%. Measurements are carried till the noise in the fluorescence signal is below 1.5%. Bold solid curves are Lorentzian fits. Optical power is adjusted in each measurement to minimize power-broadening. c Linewidth of CPT dips as a function of GS orbital splitting Δgs indicating improvement in spin coherence with increasing strain. Error bars represent standard deviation of the estimated linewidths from the Lorentzian fits. d Power dependence of CPT-linewidth at the highest strain condition (Δgs = 467 GHz). Data points are estimated linewidths from CPT measurements, and the solid curve is a linear fit, which reveals a linewidth of 0.64 ± 0.06 MHz corresponding to \(T_2^ \ast\) = 0.25 ± 0.02 μs
