  Quantum error correcting codes are designed to pinpoint exactly when and
where errors occur in quantum circuits. This feature is the foundation of their
primary task: to support fault-tolerant quantum computation. However, this
feature could used as the basis of benchmarking: By analyzing the outputs of
even small-scale quantum error correction circuits, a detailed picture can be
constructed of error processes across a quantum device. Here we perform an
example of such an analysis, using the results of small repetition codes to
determine the error rate of each qubit while idle during a syndrome
measurement. This provides an idea of the errors experienced by the qubits
across a device while they are part of the kind of circuit that we expect to be
typical in fault-tolerant quantum computers.
