So it can be as low as 3 if you're only concerned with some of the noise, but if you're trying to correct both for bit flips (0 exchanged for 1 and vice versa)

So it can be as low as 3 if you're only concerned with some of the noise, but if you're trying to correct both for bit flips (0 exchanged for 1 and vice versa) and phase drift (0 + 1 being exchanged for 0 – 1 and vice versa) then you need at least 5 physical qubits to create one logical qubit, see [wiki] for details. [wiki]: https://en.wikipedia.org/wiki/Five-qubit_error_correcting_code https://en.wikipedia.org/wiki/Five-qubit_error_correcting_co...