A UK-based physicist has published a paper in the journal Nature casting new doubt on Microsoft's claims of a breakthrough in quantum computing — arguing that a software tool used by the tech giant to verify its research contained coding errors and was not sufficiently accurate.
Dr Henry Legg, a long-term critic of Microsoft's quantum work, said the company had still not proved its assertion that it has managed to create a theoretical quasi-particle called Majorana, which underpins its entire approach to building a quantum computer.
“Dr Henry Legg published a paper in Nature questioning Microsoft's quantum computing research.”
"Last year Microsoft claimed they had built the equivalent of a precision Swiss watch. However when I opened the case to examine the mechanism, I found what looked like a chaotic jumble of mismatched parts," Legg said. "Something was making noise, but it didn't look like the breakthrough Microsoft had claimed."
Microsoft has consistently stood by its conclusions despite scepticism from experts in the field. The company has invested heavily in the race to build quantum computers, which work very differently to traditional machines and are said to have the potential to solve global challenges beyond the reach of even the world's most powerful supercomputers.
Quantum computing is already a multi-billion dollar industry despite there being only very limited devices currently in existence. Current quantum machines are prone to make mistakes in the event of the slightest interference — such as small vibrations or a tiny change in temperature.
Legg's paper critiqued research Microsoft published in 2025. The tech giant has since released a second generation of its Majorana chip, which it says is 1,000 times more reliable than the previous version.
"At the end of the day, success is the delivery of a scalable quantum computer," said Dr Chetan Nayak, Technical Fellow and Corporate Vice President, Quantum Hardware, Microsoft. "Scepticism and rigour are hallmarks of the scientific process, which we appreciate and have supported from various academics. We have participated in dialogue and our thorough rebuttal was accepted and published by Nature."
In that rebuttal, Microsoft states that the software Legg referred to did not "interpret" the measurements which led to its conclusions.
Legg also accused Microsoft of not sharing enough data for other scientists to scrutinise — the process by which scientific research is generally validated or dismissed. Microsoft said it was sharing all of its data with the US defence agency Darpa for independent arbitration but has claimed some of it is too commercially sensitive to publish more widely.
The fresh doubts come as the race to build a fully functioning quantum computer intensifies, with Microsoft among the contenders alongside rivals such as Google and IBM.