We present an analytical study on the resilience of topological order after a
quantum quench. The system is initially prepared in the ground state of the
toric-code model, and then quenched by switching on an external magnetic field.
During the subsequent time evolution, the variation in topological order is
detected via the topological Renyi entropy of order 2. We consider two
different quenches: the first one has an exact solution, while the second one
requires perturbation theory. In both cases, we find that the long-term time
average of the topological Renyi entropy in the thermodynamic limit is the same
as its initial value. Based on our results, we argue that topological order is
resilient against a wide range of quenches.Comment: 5 pages, 4 figures, published version with structural changes, see
supplemental material at
http://link.aps.org/supplemental/10.1103/PhysRevLett.110.17060
