Speaker: Dr Henry Legg (St Andrews)
Abstract:
Recently, significant attention has been focused on realising a topological qubit based on Majorana zero modes, driven in particular by claims from Microsoft Quantum. Here, I critically examine the Topological Gap Protocol (TGP) and demonstrate its fundamental Blind Spots. I show that the TGP is unreliable both as a diagnostic tool for topological superconductivity and associated Majorana zero modes, and as a method for verifying a bulk superconducting gap — a prerequisite for parity readout and qubit operation. Based on these insights, I will conclude that claims to have already realised topological qubits are not reliable and should be revisited.
References:
 [1] Hess, Legg, Loss, Klinovaja Phys. Rev. Lett. 130, 207001 (2023)
 [2] Legg, arXiv:2502.19560 (Comment accepted to PRB) [3] Legg, Nature
 654, E22–E26 (2026)