Microsoft Quantum Claims Questioned by Researcher

Quantum Computing Claims Under Scrutiny as Researcher Challenges Microsoft’s Breakthrough

Weeks after Microsoft unveiled its Majorana 2 quantum chip, touting it as a significant leap forward with 1,000 times the reliability of its predecessor and a crucial step toward practical quantum computing by 2029, a prominent researcher has cast doubt on the company’s assertions.

In a commentary published Wednesday in the journal Nature, Henry Legg, a physicist at the University of St Andrews, argued that Microsoft has failed to provide definitive proof of a topological qubit, a theoretical type of quantum bit designed to be more resilient to errors than conventional quantum computing methods.

“My critique exposing flawed tune-up procedures, code errors, and omitted data behind Microsoft’s ‘breakthrough’ quantum computing claims is published today in Nature,” Legg stated on the social platform BlueSky. “In short: Microsoft haven’t demonstrated the basic physics needed for even a single topological qubit.”

Legg’s commentary directly addresses a 2025 paper published in Nature by Microsoft Quantum researchers, which detailed evidence for the company’s topological qubit. According to Legg, the signals Microsoft attributes to this device could instead be the result of experimental noise.

“The detection of a topographical superconducting phase–the basis of proposed topological qubits–is notoriously difficult because trivial states can mimic the signatures expected from a topological superconductor,” Legg explained.

Microsoft had previously stated that Majorana 2 can maintain quantum information stability for an average of 20 seconds, with some qubits lasting up to a minute. The company credited artificial intelligence with accelerating development by identifying promising materials, automating testing, and enhancing manufacturing processes. The chip’s functionality hinges on the same topological qubit technology now facing criticism. Microsoft maintains that this approach could lead to more dependable quantum computers by mitigating the errors that currently plague existing systems.

Legg contended that previously unpublished transport data underpinning Microsoft’s findings did not clearly demonstrate the superconducting state necessary to support the company’s topological qubit claim. Instead, he suggested that the measurements appeared more consistent with alternative explanations, such as quantum dot effects.

Microsoft has pushed back against Legg’s conclusions.

“We stand by our results and our roadmap,” Chetan Nayak, Microsoft’s Technical Fellow and Corporate Vice President for Quantum Hardware, told Scientific American. Nayak highlighted Microsoft’s progression into the final phase of DARPA’s Quantum Benchmarking Initiative, which he noted followed an independent evaluation of both public and proprietary results. “Skepticism and rigor are hallmarks of the scientific process, which we appreciate and have supported from various academics,” he added.

In a formal response also published in Nature on Wednesday, Microsoft argued that its measurements support the conclusion that it has successfully produced a topological qubit. The company asserted that the stable signals observed in its experiments are consistent with a topological state and would be unlikely to arise from mere noise or a gapless state, as Legg proposed.

This debate emerges as the cryptocurrency industry actively prepares for “Q-Day,” the anticipated point at which quantum computers will possess the power to break widely used public-key cryptography. Bitcoin is considered particularly vulnerable, as a quantum attacker could potentially derive private keys from exposed public keys, leading to the theft of funds. While Legg’s critique does not negate the possibility of this future threat, it does challenge the evidence Microsoft has presented in its pursuit of achieving it.