A dispute over the topological qubit: a physicist has questioned Microsoft's key claims
The scientific community is once again at the center of a debate on quantum computing. Physicist Henry Legg from the University of St Andrews has criticized the work of Microsoft Azure Quantum, published in Nature on February 19, 2025. In his commentary, published in the same journal on June 24, he challenged the findings on which the corporation partially based its claims about creating a topological qubit.
Core of Legg's Complaints
In his critique, Legg focused on transport data from Microsoft's experimental setup. This data shows how current passes through the device and is supposed to confirm that the system is in the correct quantum state for the topological regime. In his view, the data does not demonstrate the presence of a stable superconducting gap in the areas where parity readout was performed. Without this gap, the interpretation of the signals as topological becomes shaky. Legg suggests that the observed effects could be explained by more mundane causes—for example, the influence of quantum dots or disorder within the device itself.
Microsoft's Response
Microsoft did not leave the complaints unanswered. In an official response, also published in Nature, the authors of the original study rejected the criticism. They argue that their measurements do not require a priori assumptions about the existence of a superconducting gap, and that the observed signals are fully consistent with a topological state. Chetan Nayak, Technical Director of Microsoft Quantum Hardware, stated: "We stand by our results and our roadmap." He also referenced Microsoft's participation in the prestigious DARPA US2QC program, where the company was selected for a verification phase.
Connection to Majorana 2
Notably, this dispute directly impacts the technological foundation of the new Majorana 2 chip, presented by Microsoft on June 2, 2026. Although Legg's commentary refers to a 2025 paper on InAs–Al devices (related to Majorana 1), it calls into question the foundation on which the company's entire roadmap is built. Previously, Microsoft claimed an average qubit lifetime of 20 seconds, operation speeds of about 1 μs, and plans to create a scalable quantum computer by 2029.
Physicist Sergey Frolov from the University of Pittsburgh went even further, stating that Microsoft's work in Nature likely should be retracted. This opinion underscores the seriousness of the situation, although final conclusions remain with the scientific community.
My view as an analyst: This dispute is a classic example of the tension between ambitious claims and rigorous scientific standards. If Legg's complaints are confirmed, it could significantly slow Microsoft's progress in topological qubits, which are considered one of the most promising directions for creating fault-tolerant quantum computers. Investors and enthusiasts should closely monitor developments, as the outcome of this discussion will affect not only Microsoft's reputation but also the realism of the entire quantum computing roadmap.