Author(s): Jonathan J. Thio, Songqinghao Yang, Nicole Yunger Halpern, Stephan De Bièvre, Crispin H. W. Barnes, and David R. M. Arvidsson-Shukur We elucidate the boundary between classical and quantum computation by constructing qubit Clifford circuits with nonstabilizer inputs that can be efficiently simulated classically. We do so by casting the quantum circuits realizable by defect braiding in the surface code in terms of a Kirkwood-Dirac… [Phys. Rev. Lett. 137, 080601] Published Tue Aug 18, 2026