A physicist questions Microsoft's breakthrough in topological qubits: analysis of criticism and the corporation's response
The scientific community has been stirred once again by a debate surrounding Microsoft's quantum technologies. Physicist Henry Legg from the University of St Andrews has questioned the key conclusions of a Microsoft Azure Quantum paper published in Nature in February 2025, on which the corporation based its claims of creating a topological qubit. Legg presented his critical analysis in the same journal on June 24, to which Microsoft promptly responded, defending its results.
A topological qubit is a theoretically more stable type of quantum bit that should be more resistant to errors due to a special way of storing information. It is precisely this stability that Legg is calling into question.
The Essence of Legg's Criticism
At the center of the dispute are the transport data from Microsoft's 2025 work. These data show how current flows through the experimental device and are supposed to confirm that the system is in the desired topological quantum state. Legg argues that these data do not confirm the presence of a stable superconducting gap in the regions where Microsoft performed parity readout. Without this gap, he contends, the interpretation of the measurements as topological becomes shaky.
Furthermore, Legg suggests that the observed signals could be explained by much simpler effects—the influence of quantum dots or the disorder of the device itself. In simple terms, he believes Microsoft may have mistaken ordinary, non-topological states for the long-awaited regime.
Microsoft's Response and Expert Positions
Microsoft categorically rejected the criticism. In their response in Nature, the authors stated that their measurements do not require a prior assumption about the presence of a gap, and that all observed signals are fully consistent with the topological state. Chetan Nayak, Technical Director of Microsoft Quantum Hardware, supported this position, stating: "We stand by our results and our roadmap." As an indirect argument, the corporation cites its participation in the prestigious DARPA program, which selected Microsoft for a verification phase under an initiative to build an industrially useful quantum computer by 2033.
However, physicist Sergey Frolov from the University of Pittsburgh took a harsher stance, stating that Microsoft's work in Nature should likely be retracted. This dispute does not directly concern the new Majorana 2 chip, unveiled in June 2026, but it does affect the very technological foundation on which Microsoft's entire roadmap is built.
My analysis: This dispute is a classic example of the tension between ambitious claims and rigorous scientific verification in quantum physics. While Microsoft confidently moves toward commercialization, Legg's criticism serves as a reminder that the path to a true topological qubit is still strewn with ambiguous data. Investors and observers should closely monitor the development of this discussion, as the outcome will determine trust in the technological foundation of one of Microsoft's most promising directions.