Researchers have demonstrated a new control principle for manipulating topological corner states, a crucial advance for the development of quantum technologies. Using the two-dimensional Benalcazar-Bernevig-Hughes (BBH) model as an example, they have discovered that subchiral symmetry allows for the controllable creation, isolation, and transfer of these modes. These states, inherent to higher-order topological phases, promise robustness against perturbations, but their practical utility depended on precise manipulation, which was previously a challenge.

The study reveals that conventional chiral symmetry decomposes into four subchiral symmetries, each associated with a zero-energy corner mode. By selectively breaking these subsymmetries with controlled intercell hoppings, the scientists managed to reduce the fourfold corner-state manifold to single, isolated modes. This step-by-step control is fundamental for engineering quantum systems that require the interaction or isolation of specific states.

Furthermore, the team designed adiabatic protocols capable of transferring either a single corner state or a superposition of two corner states between selected corners, preserving the relative phase in the latter case. Both numerical simulations and implementations on an IBM quantum processor confirmed the high fidelity of these protocols. This work establishes subchiral symmetry as a promising route for programmable manipulation of higher-order topological states, opening new possibilities for quantum computing and quantum sensing.