Methods, systems and apparatus for correcting a stream of syndrome measurements produced by a quantum computer. A layered representation of error propagation through quantum error detection circuits is received. The layered representation includes a plurality of line circuit layers that each represent a probability of local detection events in a quantum computer associated with one or more potential error processes in the execution of a quantum algorithm. During execution of the quantum algorithm, one or more syndrome measurements are received from quantum error detection circuits. The syndrome measurements are converted into detection events and written to an array that represents quantum error correction circuits that are grouped together at a sequence of steps in the quantum algorithm. Errors in the execution of the quantum algorithm are determined from the detection events in dependence upon the stored line circuit layers. Based on the determined errors, the syndrome measurements are corrected.