Abstract: Methods, systems, and techniques for detecting errors in qubits within a quantum computing system. In at least one embodiment, at least one quantum check operator is used to couple data qubits with syndrome qubits, a parity-check code is used to couple the syndrome qubits with measure qubits, and the measure qubits are measured to determine whether any errors are present in the data qubits. In at least one embodiment, codewords are coupled to one or more ancilla qubits based at least in part on a binary matrix associated with one or more non-Calderbank-Shor-Steane (“non-CSS”) quantum codes, and the one or more ancilla qubits are used to obtain information about any errors present in the codewords.

Abstract: A quantum computing system and associated methods. An exemplary method includes generating a specification from a binary matrix and at least one quantum check operator. The binary matrix is based at least in part on a classical error correcting code and the quantum check operator(s) is/are based on at least one multiple-qubit Pauli operator. The specification indicates which ancilla qubits are to be coupled to which data qubits. The data qubits are prepared as a plurality of multiple-qubit entangled states. The exemplary method also includes directing quantum hardware components of the quantum computing system to couple each of selected ones of the data qubits to one or more of the ancilla qubits in accordance with the couplings indicated in the specification. Each of the plurality of multiple-qubit entangled states is coupled to a plurality of the ancilla qubits.