Microsoft and Nokia are developing a contentious new type of quantum computer
Yesterday, three members of Microsoft's quantum team presented their work towards a topological quantum computer at the APS Global Summit in Anaheim. Last month, the team made waves announcing their first topological quantum chip, the Majorana 1. More quietly, Nokia Bell Labs has been working on their own version of a topological quantum computer, and the company claims it's demonstrated the key ingredients in 2023. Both efforts represent scientific achievements, but bulletproof evidence of a topological quantum bit is elusive. "I would say all quantum computing is early stages," says Bertrand Halperin, emeritus professor of physics at Harvard, who is not involved in either effort. "But topological quantum computing is further behind. It could catch up; it's taking a somewhat different path." What's a Topological Quantum Computer? Quantum computers run on qubits valued at 0, 1, or some superposition of the two, usually encoded through some local quantum property—say, whether an electron's spin is up or down. This gives quantum computers different capabilities than their classical cousins, promising to easily crack certain types of problems that are out of reach of even the largest supercomputers. The issue is that these quantum superpositions are very fragile. Any noise in the environment, be it temperature fluctuations or small changes in electric or magnetic fields, can knock qubits out of superposition, causing errors. Topological quantum computing is a fundamentally different approach to building a qubit, one that in theory would be a much less fragile. The idea is that instead of using some local property to encode the qubit, you would use a global, topological property of a whole sea of electrons. Topology is a field of mathematics that deals with shapes: Two shapes are topologically identical if they can be transformed into each other without tearing new holes or connecting previously unconnected ends. For example, an infinite rope extending into space…