Our paper, Optical one-way quantum computing with a simulated valence-bond solid, by Rainer Kaltenbaek, Jonathan Lavoie, Bei Zeng (U Guelph), Stephen D. Bartlett (U Sydney), and Kevin J. Resch was published online today at Nature Physics. Robert Raussendorf (U British Columbia), who invented measurement-based quantum computing with Hans Briegel (U Innsbruck), wrote a great News and Views article describing our work and issuing new challenges to the community.
One-way quantum computation proceeds by sequentially measuring individual spins in an entangled many-spin resource state. It remains a challenge, however, to efficiently produce such resources. Is it possible to reduce the task of their production to simply cooling a quantum many-body system to its ground state? Cluster states, the canonical resource for one-way quantum computing, do not naturally occur as ground states of physical systems, leading to a significant effort to identify alternatives that do appear as ground states in spin lattices. An appealing candidate is a valence-bond solid state described by Affleck, Kennedy, Lieb and Tasaki (AKLT). It is the unique, gapped ground state for a two-body Hamiltonian on a spin-1 chain, and can be used as a resource for one-way quantum computing. Here, we experimentally generate a photonic AKLT state and use it to implement single-qubit quantum logic gates.