Perturbative tomography of small errors in quantum gates
Ruyu Yang, Ying Li · Physical Review A · 2021
We propose an efficient protocol to fully reconstruct a set of high-fidelity quantum gates. Usually, the efficiency of reconstructing high-fidelity quantum gates is limited by the sampling noise. Our protocol is based on a perturbative approach and has two stages. In the first stage, the unital part of noisy quantum gates is reconstructed by measuring traces of maps, and the trace can be measured by amplifying the noise in a way similar to randomized benchmarking and quantum spectral tomography. In the second stage, by amplifying the nonunital part using the unital part, we can efficiently reconstruct the nonunital part. We show that the number of measurements needed in our protocol scales logarithmically with the error rate of gates.