Depends what you mean by qbit. If you are including a magic state factory in your architecture then lots and lots (millions). If you mean stable qbits then I've

Depends what you mean by qbit. If you are including a magic state factory in your architecture then lots and lots (millions). If you mean stable qbits then I've been told that 4096 bit numbers could be factored with 8000 qbits that are very stable and can be operated on frequently.