Code switching revisited: low-overhead magic state preparation using color codes

Oct 9, 2024
11 pages
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Abstract: (arXiv)
We propose a protocol to prepare a high-fidelity magic state on a 2D color code using a 3D color code. Our method modifies the known code switching protocol with (i) a transversal gate between the 2D and the 3D code and (ii) a judicious use of flag-based post-selection. We numerically demonstrate that these modifications lead to a significant improvement in the fidelity of the magic state. For instance, subjected to a uniform circuit-level noise of 10310^{-3}, our code switching protocol yields a magic state encoded in the distance-33 2D color code with a logical infidelity of 4.6×105±1.6×1054.6\times 10^{-5}\pm 1.6 \times 10^{-5} (quantified by an error-corrected logical state tomography) with a 84%84\% of acceptance rate. Used in conjunction with a more recently proposed post-selection approach, extrapolation from a polynomial fit suggests a fidelity improvement to 5.1×1075.1 \times 10^{-7} for the same code. Finally, we also present a novel simulation technique akin to an extended stabilizer simulator which effectively incorporates the non-Clifford TT-gate.
Note:
  • 11 pages, 9 figures. v2: minor changes