IQI Weekly Seminar

Can the properties of the thermodynamic limit of a many-body quantum system be extrapolated by analyzing a sequence of finite-size cases? We present models with relatively low local Hilbert space dimensions for which such an approach gives completely misleading results: a translationally invariant local Hamiltonian on a square lattice with constant spectral gap and classical product ground state for system sizes smaller than a threshold, and a ground state with topological degeneracy for larger system sizes. The resulting effect may be viewed as a new type of quantum phase transition that is driven by the size of the system rather than by a local field or coupling.

(joint work with Toby S. Cubitt, Angelo Lucia, David Perez-Garcia, Michael M. Wolf; http://arxiv.org/abs/1512.05687)