Physicist challenges Microsoft's topological qubit claims

A peer-reviewed paper published in Nature on Wednesday challenges the scientific foundation of Microsoft's quantum computing breakthrough announced last year. Henry Legg, a physicist at the University of St Andrews, reanalyzed the data behind Microsoft's Majorana 1 chip and concluded the company did not conclusively demonstrate a working topological qubit.

Microsoft unveiled the Majorana 1 processor in February 2025, positioning it as a breakthrough in quantum computing technology. The company described topological qubits as the "building blocks" for their future quantum computer and has since announced a second-generation chip, Majorana 2, at Build earlier this month.

The technical dispute

Microsoft's approach to quantum computing differs from competitors like Google and IBM. The Majorana design uses a wire thinner than a human hair, made from indium arsenide semiconductor bonded to a superconductor. According to theory, electrons in this wire should behave in a collective pattern known as a Majorana particle, which gives the chip its name. Microsoft aims to encode quantum information in the properties of these Majorana particles.

Legg's critique, which underwent peer review before publication in Nature, takes issue with whether Microsoft's experimental data actually proves the existence of these topological qubits. Microsoft has disputed the findings.

Why it matters

The stakes extend beyond academic debate. Topological qubits represent Microsoft's chosen path toward practical quantum computing, distinguishing its strategy from competitors who have already demonstrated more advanced machines using different approaches. While no company has yet built a quantum computer that performs useful work, the validity of Microsoft's foundational technology affects its credibility in the race to achieve quantum advantage. For enterprise technology leaders evaluating quantum computing investments and partnerships, understanding which technical approaches rest on solid experimental evidence matters for long-term planning.

The broader quantum landscape

Quantum computing proponents predict the technology will accelerate drug discovery, advance encryption capabilities, and improve machine learning. Google and IBM have built more advanced quantum systems than Microsoft's Majorana chips, though no quantum computer has yet conclusively performed useful computational work that classical computers cannot match.

Microsoft continues to advance its roadmap despite the critique, having already announced the Majorana 2 chip. The company maintains its position that the original data supports its topological qubit claims.

The Verge first reported these details.