Riverlane's founder and CEO, Steve Brierley, told Ars that error correction doesn't only stress the qubit hardware; it stresses the classical portion of the system as well. Each of the measurements of the qubits used for monitoring the system needs to be processed to detect and interpret any errors. We'll need roughly 100 logical qubits to do some of the simplest interesting calculations, meaning monitoring thousands of hardware qubits. Doing more sophisticated calculations may mean thousands of logical qubits.

That error-correction data (termed syndrome data in the field) needs to be read between each operation, which makes for a lot of data. "At scale, we're talking a hundred terabytes per second," said Brierley. "At a million physical qubits, we'll be processing about a hundred terabytes per second, which is Netflix global streaming."

Both of these versions are highly specialized; they simply feed the error information for other parts of the system to act on. So, it is a highly focused solution.