Fig. 4: Error mitigation results for different qubit–TLS modulation strategies.
From: Error mitigation with stabilized noise in superconducting quantum processors
a–c Weight-6 observable (〈ZZZZZZ〉) estimates as a function of time using the three different strategies with (filled markers) and without (open markers) error mitigation, along with the cumulative average of the mitigated observable values (solid line). The experiment is performed following the schedule described in Fig. 2 for the a control, b optimized, and c averaged modulation strategies. For reference, the ideal observable of 1 is indicated as a dashed line. The mitigated observables can be seen to fluctuate near the ideal value, and the shaded regions highlight time windows with high fluctuations as determined by the analysis in Fig. 2d. Each data point is obtained from 4096 random circuit instances with 32 shots per circuit. During the experiment, we interleave 2048 random circuit instances for readout-error mitigation38 and 512 random circuit instances for estimating the unmitigated observable. Readout-error mitigation is applied to both the unmitigated and mitigated observable estimates. Error bars for the unmitigated and mitigated results are obtained by bootstrapping the PEC result 25 times. d–f Scatter plots of the predicted (δpred) and observed (δmit) deviations of the observable from the ideal expectation value. The correlation between δpred and δmit confirms that the temporal fluctuation of the noise model plays a role in the mitigation error observed in the PEC protocol. The histograms along the y-axis show the respective distributions of δmit.
