This task is possible for a set of operators E if inner products of the form (*) "bra-psi E-sub-i-dagger E-sub-j ket psi" are elements of an Hermitian matrix, by the Knill-Laflamme conditions. A class of methods for this task are named for abelian subgroups of the Pauli group P-sub-n whose elements share an invariant subspace, exemplified by the CSS method. The star and planchette operators are the stabilizers in a square lattice model that performs this task by annihilating anyonic (“any-onic”) excitations. Schemes for this task with distance 3, 5, and 7 were implemented (15[1])on Google’s Willow chip in the first demonstration of the threshold theorem. Logical qubits require multiple physical qubits because the auxiliary qubits perform this task. For 10 points, Shor’s code is a method for what task that involves fixing phase flips and bit (15[1])flips? ■END■