Of course 3 nines of reliability in directly processing information is not very useful; after ~1000 operations you would be very likely to have an error. But qu

Of course 3 nines of reliability in directly processing information is not very useful; after ~1000 operations you would be very likely to have an error. But quantum computers do not process information that is stored in single qubits. They use quantum error correction to turn many mediocre qubits (i.e. 3 nines) into a smaller number of very good (like 18 nines) error-corrected logical qubits. These error correcting codes work fine with 3 or 4 nines. In fact I'm not aware of any platform that plans to scale by reaching 5 nines. Everyone is aiming for the 3-4 nines regime. Incidentally, quantum error correction is the reason why you need 1 million qubits to factor as RSA number. Shor's algorithm only needs Few thousand, but error correction adds lot of overhead.