Theory shows broken mirror symmetry enables universal control of globally driven qubit chains
Hong-Ye Hu and colleagues developed a theory of universal control for globally driven quantum systems, with the study forthcoming in Nature Physics (the linked manuscript is the authors' preprint, not yet peer reviewed). For a one-dimensional qubit chain with uniform nearest-neighbor interactions and global rotations, the team proves that adding a controllable field or interaction that breaks mirror symmetry makes universal quantum control possible, and they extend related results to fermionic and bosonic systems. Using a method they call direct quantum optimal control, which accounts for laser limits and atomic motion, they produced an effective three-atom ZXZ interaction in a Rydberg-atom array. In an eight-atom chain (physical atoms, not logical qubits), end atoms retained distinctive signals and correlations, which the authors describe as a signature of topological edge modes.