Crystalline phases and devil's staircase in qubit spin ice
Abstract: Motivated by the recent realization of an artificial quantum spin ice in an array of superconducting qubits with tunable parameters, we scrutinize a quantum six-vertex model on the square lattice that distinguishes type-I and type-II vertices. We map the zero-temperature phase diagram using numerical and analytical methods. Following a symmetry classification, we identify three crystalline phases alongside a subextensive manifold of isolated configurations.