Comment by upofadown

The idea seems to be that there will some sort of cascading effect if we can somehow create physical qubits with sufficient noise performance. It's this "threshold" we keep hearing about. Once we exceed threshold there is a possibility that we can use error correction to expand everything without limit.

This assumes that there will not be other problems that arise. I suspect that "error correcting" thousands of qubits entangled with one another will be one of those problems.