Topological qubit
Microsoft's long game — qubits where information is stored in the system's shape rather than in individual particles, and so protected from the outset.
The idea is to encode the state in topological properties of exotic quasiparticles known as Majorana states. Because the information is not stored locally, local disturbances cannot destroy it — error correction would be built into the physics instead of costing a thousand physical qubits per logical one.
It is the most ambitious and least confirmed route. Microsoft has worked on it for over two decades, and the field carries a retracted 2018 paper on the observation of Majorana states. The company presented its Majorana 1 chip in 2025 with claims the research community is still debating. If it works it is a large leap; if not, a great deal of time will have gone into a dead end.