A dispute over the topological qubit: a physicist questions Microsoft's breakthrough
A serious scientific debate is heating up in the world of quantum computing. Physicist Henry Legg from the University of St Andrews has questioned key conclusions of a Microsoft Azure Quantum paper published in February 2025. This work underpinned the company's claims about creating a topological qubit — one of the most promising yet most challenging types of quantum bits.
Legg analyzed the transport data presented in the Microsoft paper. This data shows how electric current passes through the experimental device and allows conclusions about the quantum state of the system. In his view, the data does not confirm the presence of a stable superconducting gap in the areas where Microsoft performed parity readout. The absence of such a gap casts doubt on the interpretation of the measurements as topological.
The physicist suggests that the observed signals may have a more mundane explanation — for example, effects from quantum dots or disorder within the device itself. Simply put, Legg argues that Microsoft may have mistakenly interpreted non-topological states as signs of the desired topological regime.
Microsoft's Position and Response to Criticism
Microsoft Corporation has categorically rejected the criticism. In an official response, also published in Nature, the paper's authors stated that their measurements do not require a prior assumption about the existence of a superconducting gap. They insist that the signals are consistent with a topological state. Microsoft Quantum Hardware Technical Director Chetan Nayak expressed full confidence in the results: "We stand behind our results and our roadmap."
As an argument, Nayak cited Microsoft's participation in the prestigious DARPA US2QC program. In February 2025, the agency selected Microsoft and PsiQuantum for the verification and co-design phase. This program is part of the broader Quantum Benchmarking Initiative, which aims to assess the feasibility of building an industrially useful quantum computer by 2033.
Connection to the New Majorana 2 Chip
This dispute is particularly significant in light of Microsoft's recent announcement. In June 2026, the company unveiled Majorana 2 — a new generation of topological quantum chip. According to the statement, the average qubit lifetime reached 20 seconds, and in some cases, a minute. The company also reported an operation speed of about 1 microsecond and a qubit size of approximately 0.01 mm, setting a goal to create a scalable quantum computer by 2029. The progress is attributed to replacing aluminum with lead in the superconducting layer and using Microsoft Discovery AI tools.
It is important to understand that Legg's commentary is not a direct analysis of Majorana 2. It concerns the 2025 paper on InAs–Al devices, related to the previous generation — Majorana 1. However, this dispute touches on the very technological foundation upon which Microsoft's new roadmap is built. Physicist Sergey Frolov from the University of Pittsburgh even stated that the Microsoft paper in Nature likely should be retracted.
Analyst's opinion. This dispute is a classic example of how, in science — especially at the forefront of quantum technologies — ambitious claims often outpace irrefutable evidence. For the crypto community, this is a signal: one should not perceive any "breakthroughs" as an immediate threat to existing cryptographic algorithms. The path to an industrially useful quantum computer remains long and arduous, and any achievement along this path will undergo the most thorough and skeptical scrutiny.