Demonstrating the effectiveness of error mitigation protocols based on efficient noise reconstruction

Despite the unprecedented technological advances in the development of quantum computing platforms seen in recent years, fault-tolerance remains too demanding. Thus, developing alternative strategies to improve the performance of the noisy devices currently available is of timely importance. To tackle this problem we provide two error mitigation protocols (named ``Quasi-Probabilistic Protocol'' and ``Cycle Extrapolation'') that can significantly upgrade the performance of the cycles of gates applied in experimental setups. By combining popular mitigation strategies such as error cancellation and noise amplification with the efficient noise reconstruction methods developed by the Quantum Benchmark team at Keysight Technologies, our protocols can mitigate a wide range of noise processes that afflict today's devices, including non-local and gate-dependent processes. We demonstrate our protocols on a superconducting processor at Berkeley Lab. Our experiments show significant improvements for structured circuits, such as circuits preparing W states or implementing the quantum phase estimation algorithm, as well as for random circuits. Overall, our work demonstrates a practical and reliable toolkit to characterise and mitigate the noise afflicting today's devices.