[Show abstract][Hide abstract] ABSTRACT: Scalable quantum computing can be achieved only if quantum bits are manipulated in a fault-tolerant fashion. Topological error correction--a method that combines topological quantum computation with quantum error correction--has the highest known tolerable error rate for a local architecture. The technique makes use of cluster states with topological properties and requires only nearest-neighbour interactions. Here we report the experimental demonstration of topological error correction with an eight-photon cluster state. We show that a correlation can be protected against a single error on any quantum bit. Also, when all quantum bits are simultaneously subjected to errors with equal probability, the effective error rate can be significantly reduced. Our work demonstrates the viability of topological error correction for fault-tolerant quantum information processing.
[Show abstract][Hide abstract] ABSTRACT: The creation of increasingly large multipartite entangled states is not only a fundamental scientific endeavour in itself1-3, but is also the enabling technology for quantum information4,5. Tremendous experimental effort has been devoted to generating multiparticle entanglement with a growing number of qubits6-16. So far, up to six spatially separated single photons10-14 have been entangled based on parametric downconversion17. Multiple degrees of freedom of a single photon have been exploited to generate forms of hyper-entangled states18,19. Here, using new ultra-bright sources of entangled photon pairs20, an eight-photon interferometer and post-selection detection, we demonstrate for the first time the creation of an eight-photon Schrödinger cat state 1 with genuine multipartite entanglement. The ability to control eight individual photons represents a step towards optical quantum computation, and will enable new experiments on, for example, quantum simulation 21,22, topological error correction23 and testing entanglement dynamics under decoherence24.