A physicist has cast doubt on a test that underlies a high-profile claim by Microsoft to have created the first ‘topological qubits’, a long-sought goal of the company’s quantum-computing effort. The critique comes amid mounting speculation about the validity of Microsoft’s claim. Microsoft announced the breakthrough, which could lead to a quantum computer that is more resistant to information loss than with other approaches, on 19 February. Without a peer-reviewed paper backing up the claim, some researchers were sceptical. An accompanying paper in Nature described a method to measure the read-out from future topological qubits, but did not offer proof of their existence1. “While the Nature paper outlined our approach, it does not speak to our progress,” a Microsoft spokesperson said in a statement. The paper was submitted almost a year before it was published and since then “tremendous progress has occurred”, they said. In the latest critique, posted as a preprint2, Henry Legg, a theoretical physicist at the University of St Andrews, UK, raises concerns about a test that Microsoft uses to look for Majoranas, so-far undiscovered quasiparticles arising from the collective behaviour of electrons that are needed for the topological qubits to work.

Full report : Researchers have criticised Microsoft’s new Majorana 1 quantum computer, saying the company has made claims about the way it works that aren’t fully backed up by scientific evidence.