Fig. 2: Ultrafast coherent spin control of mode A.
From: Ultrafast coherent control of a hole spin qubit in a germanium quantum dot
a Schematic representation of the spin manipulation cycle and corresponding gate-voltage (VR) modulation pattern. The spin state is first initialized at point I in the PSB regime (Fig. 1b). A pulse then detunes the state to point M in the Coulomb blockade regime for spin manipulation. During this step, a microwave burst with a duration of τburst is applied to generate spin rotation via EDSR. Afterwards, the system is shifted from Coulomb blockade regime back to spin blockade regime at point R for readout. b At an external magnetic field of B = 100 mT, spin oscillation is observed by sweeping the microwave frequency f and microwave duration time τburst (the amplitude from the pulse signal generator is set at P = −15 dBm) applied to the gate R. Each data point is averaged over 20 repetitions. c Rabi oscillations at f = 7.92 GHz with a fit to \({{{\rm{A}}}}\cdot\cos(2{{{{{\rm{\pi }}}}}}{\it{f}}_{{{{{{\rm{Rabi}}}}}}}{\tau }_{{{{{{\rm{burst}}}}}}}+{\it{\varphi}} )\cdot \exp (-{({\tau }_{{{{{{\rm{burst}}}}}}}/{\it{T}}_{2}^{{{{{{\rm{R}}}}}}})}^{2})+{\it{I}}_{0}\) (An offset of 0.5 pA is set between two oscillations for clarity). Rabi frequencies are 112 ± 2, 202 ± 2 and 393 ± 2 MHz from bottom to top. We correct the data by removing the background current I0. Similar results for mode B are shown in Supplementary Fig. 7.1. To mitigate the effects of charge noise, we average the current over 100 repeated cycles for each data point (Supplementary Fig. 5). d Rabi oscillations under different microwave power P.
