Detecting Non-Markovian Errors in Superconducting Qubit Operations Using Partial Tomography*

With recent progress in materials and qubit design, the coherence times of superconducting qubits have been improved to 0.1 - 1 ms [1,2]. Since the gate fidelity of superconducting qubits is typically limited by decoherence, these advancements have resulted in single-qubit error rates below 10^-4 and two-qubit gates below 10^-3 [2-5]. With further improvements in coherence times, the fidelity of qubit operations could enter a regime no longer limited by qubit coherence and the dominant operational errors may be non-Markovian. To anticipate this progress, we introduce a novel characterization scheme based on partial tomography that can reconstruct error channels without assuming Markovian noise. We leverage this method to measure quasi-static noise, crosstalk and context-dependent coherent errors, which are considered to be among the most common non-Markovian errors in superconducting qubits [6,7]. With numerical simulations and experiments we show how this novel protocol can help to understand and mitigate correlated errors in superconducting qubits.

 

[1] A.P.M. Place et al., Nat. Commun 12., 1779 (2021).

[2] A. Somoroff et al., Phys. Rev. Lett. 130, 267001 (2023).

[3] Z. Li et al., arXiv 2302.08690 (2023).

[4] L. Ding et al., arXiv 2304.06087 (2023).

[5] H. Zhang et al., arXiv 2309.05720 (2023).

[6] D.M. Debroy et al., arXiv 2303.17565 (2023).

[7] M. Papič et al., arXiv 2305.08916 (2023).