Symmetric Finite-Time Preparation of Cluster States via Quantum Pumps

It has recently been established that clusterlike states - states that are in the same symmetry-protected topological phase as the cluster state - provide a family of resource states that can be utilized for measurement-based quantum computation. In this Letter, we ask whether it is possible to prepare clusterlike states in finite time without breaking the symmetry protecting the resource state. Such a symmetry-preserving protocol would benefit from topological protection to errors in the preparation. We answer this question in the positive by providing a Hamiltonian in one higher dimension whose finite-time evolution is a unitary that acts trivially in the bulk, but pumps the desired cluster state to the boundary. Examples are given for both the 1D cluster state protected by a global symmetry, and various 2D cluster states protected by subsystem symmetries. We show that even if unwanted symmetric perturbations are present in the driving Hamiltonian, projective measurements in the bulk along with feed-forward correction is sufficient to recover a clusterlike state.