Quantum codes correct errors even with qubit loss or gain

More than a half-century after the classical discovery of an equivalence between insertion and deletion errors, researchers at the University of Sheffield have made progress towards a quantum counterpart, addressing a longstanding problem in quantum error correction. Lewis Bulled and Yingkai Ouyang detail the conditions under which permutation-invariant codes can correct errors that simultaneously delete and insert qubits, a more complex scenario than addressing each error type separately. Their work resolves many outstanding questions regarding the quantum error correction of synchronisation errors, which change the number of qubits in a quantum system. The researchers formulate conditions under which these codes are (t,s)-insdel error-correctable. Permutation-invariant codes can now correct errors arising from both the…