Suppressing quantum errors by scaling a surface code logical qubit

Practical quantum computing will require error rates well below those achievable with physical qubits. Here we report measurement of logical qubit performance scaling across several code sizes, and demonstrate that our system of superconducting qubits has sufficient performance to overcome additional errors from increasing qubit number. Distance-5 surface code logical qubit modestly outperforms an ensemble of distance-3 logical qubits: (2.914±0.016)% vs (3.028±0.023)% logical error per cycle.