[kamilner]

QEC implies phase error correction (if you don't care about phase errors you could just use a classical error correction code). A 'logical qubit' refers to an abstraction layer that implements some sort of idealized qubit behaviour (including the phase) that is used as a qubit in computation without considering the underlying implementation. The underlying implementation of a single logical qubit may be something like 5 'physical qubits' using https://en.wikipedia.org/wiki/Five-qubit_error_correcting_co... or a entire structure of many physical qubits using something like a https://en.wikipedia.org/wiki/Toric_code