Efficient benchmarking of logical magic state

ORAL

Abstract

High-fidelity logical magic states are a critical resource for fault-tolerant quantum computation, enabling non-Clifford logical operations through state injection. However, benchmarking these states presents significant challenges: one must estimate the infidelity $\epsilon$ with multiplicative precision, while many quantum error-correcting codes only permit Clifford operations to be implemented fault-tolerantly. Consequently, conventional state tomography requires $\sim1/\epsilon^2$ samples, making benchmarking impractical for high-fidelity states. In this work, we show that any benchmarking scheme measuring one copy of the magic state per round necessarily requires $\Omega(1/\epsilon^2)$ samples for single-qubit magic states. We then propose two approaches to overcome this limitation: (i) Bell measurements on two copies of the twirled state and (ii) single-copy schemes leveraging twirled multi-qubit magic states. Both benchmarking schemes utilize measurements with stabilizer states orthogonal to the ideal magic state, and we show that $O(1/\epsilon)$ sample complexity is achieved, which we prove to be optimal. Finally, we demonstrate the robustness of our protocols through numerical simulations under realistic noise models, confirming that their advantage persists even at moderate error rates currently achievable in state-of-the-art experiments.

*S.L., M.Y., S.C., and L.J. acknowledge support from the ARO(W911NF-23-1-0077), ARO MURI (W911NF-21-1-0325), AFOSR MURI (FA9550-21-1-0209, FA9550-23-1-0338), DARPA (HR0011-24-9-0359, HR0011-24-9-0361), NSF (ERC-1941583, OMA-2137642, OSI-2326767, CCF-2312755, OSI-2426975), and the Packard Foundation (2020-71479). K.T. is supported by the Program for Leading Graduate Schools (MERIT-WINGS), JST BOOST Grant Number JPMJBS2418, JST ASPIRE Grant Number JPMJAP2316, and JST ERATO Grant Number JPMJER2302. S.L. is partially supported by the Kwanjeong Educational Foundation. We are also grateful for the support of the University of Chicago's Research Computing Center for assistance with the calculations carried out in this work.

Publication: Su-un Lee, Ming Yuan, Senrui Chen, Kento Tsubouchi, and Liang Jiang, Efficient benchmarking of logical magic state (2024), arXiv:2505.09687 [quant-ph].

Presenters

  • Su-un Lee

    • University of Chicago

Authors

  • Su-un Lee

    • University of Chicago
  • Ming Yuan

    • University of Chicago
  • Senrui Chen

    • University of Chicago
  • Kento Tsubouchi

    • The University of Tokyo
  • Liang Jiang

    • University of Chicago