  Topological error correction--a novel method to actively correct errors based
on cluster states with topological properties--has the highest order of
tolerable error rates known to date (10^{-2}). Moreover, the scheme requires
only nearest-neighbour interaction, particularly suitable for most physical
systems. Here we report the first experimental demonstration of topological
error correction with an 8-qubit optical cluster state. In the experiment, it
is shown that a correlation can be protected against a single error on any
single qubit. In addition, when all qubits are simultaneously subjected to
errors with equal probability, the effective error rate is significantly
reduced, clearly verifying the advantage of topological error correction. The
quantum gate with the error rate below the threshold is within the current
experimental technology. We believe topological error correction should be a
critical ingredient for the future large-scale quantum computation.
