Fig. 3: Residual \(\left|e\right\rangle\) state population measurement and improvement of the readout fidelity.

a Residual \(\left|e\right\rangle\) population measurement with Reference (red) and Signal (blue) Rabi oscillations with solid sinusoidal fitting curves. From the fitting, two Rabi amplitudes(A_sig and A_ref) can be extracted. The Reference and Signal pulse sequences are shown in the upper left corner. P1 and P2 are two measured points in b. b \(\left|e\right\rangle\) population measurement with different parametric reset pulse duration τ. Each data point is acquired by a "two-point method" described in the main text. At 34 ns, the population of the \(\left|e\right\rangle\) decays to the first minimum value 0.08 ± 0.08% and remains below 0.1% after 1000 ns. The error bars are statistical ( ± 1 s.d.) with 50 repetitions. c Readout fidelity enhancement with the 34 ns parametric reset pulse. The circles (squares) display the IQ analysis with (without) the 34 ns parametric pulse. Both \(\left|g\right\rangle\) (blue) and \(\left|e\right\rangle\) (red) are prepared and measured. When preparing the \(\left|g\right\rangle\) state, the residual \(\left|e\right\rangle\) state population due to the thermal excitation decreases more than one order of magnitude after applying the parametric reset pulse. The readout fidelity consequently improves from 96.13% to 99.43% for \(\left|g\right\rangle\) and 92.69% to 96.05% for \(\left|e\right\rangle\) respectively.