Comment on "InAs-Al hybrid devices passing the topological gap protocol", Microsoft Quantum, Phys. Rev. B 107, 245423 (2023)

Abstract

The topological gap protocol (TGP) is presented as "a series of stringent experimental tests" for the presence of topological superconductivity and associated Majorana zero modes. Here, we show that the TGP, "passed" by Microsoft Quantum [PRB 107, 245423 (2023)], lacks a consistent definition of "gap" or "topological", and even utilises different code when applied to theoretical simulations compared to experimental data. Furthermore, the outcome of the TGP is sensitive to the choice of magnetic field range, bias voltage range, data resolution, and cutter voltage pair (junction transparency) -- data parameters that, in PRB 107, 245423 (2023), vary significantly, even for measurements of the same device. As a result, the core claims of PRB 107, 245423 (2023) are based on unexplained measurement choices and inconsistent definitions. In particular, this means the claim by Microsoft Quantum in PRB 107, 245423 (2023) that their devices have a "high probability of being in the topological phase" is not reliable and should be revisited. In light of this, subsequent studies that are based on tuning up devices via the TGP should also be revisited.