Absorption-Emission Codes for Atomic and Molecular Quantum Information Platforms.

Diatomic molecular codes [V. V. Albert, J. P. Covey, and J. Preskill, Robust encoding of a qubit in a molecule, Phys. Rev. X 10, 031050 (2020).PRXHAE2160-330810.1103/PhysRevX.10.031050] are designed to encode quantum information in the orientation of a diatomic molecule, allowing error correction from small torques and changes in angular momentum. Here, we directly study noise native to atomic and molecular platforms-spontaneous emission, stray electromagnetic fields, and Raman scattering-and show that diatomic molecular codes fail against this noise. We derive simple conditions that are sufficient for codes to protect against such noise. We also identify existing and develop new absorption-emission (Æ) codes that are more practical than molecular codes, require lower average momentum, can directly protect against photonic processes up to arbitrary order, and are applicable to a broader set of atomic and molecular systems.