Relaxation times do not capture logical qubit dynamics

Understand

Quantum error correction procedures have the potential to enable faithful operation of large-scale quantum computers.

• They protect information from environmental decoherence by storing it in logical qubits, built from ensembles of entangled physical qubits according to suitably tailored quantum error correcting encodings.
• To date, no generally accepted framework to characterise the behaviour of logical qubits as quantum memories has been developed.
• In this work, we show that generalisations of well-established figures of merit of physical qubits, such as relaxation times, to logical qubits fail and do not capture dynamics of logical qubits.