  We report the characterization of a universal set of logic gates for one-way
quantum computing using a four-photon `star' cluster state generated by fusing
photons from two independent photonic crystal fibre sources. We obtain a
fidelity for the cluster state of 0.66 +/- 0.01 with respect to the ideal case.
We perform quantum process tomography to completely characterize a
controlled-NOT, Hadamard and T gate all on the same compact entangled resource.
Together, these operations make up a universal set of gates such that arbitrary
quantum logic can be efficiently constructed from combinations of them. We find
process fidelities with respect to the ideal cases of 0.64 +/- 0.01 for the
CNOT, 0.67 +/- 0.03 for the Hadamard and 0.76 +/- 0.04 for the T gate. The
characterisation of these gates enables the simulation of larger protocols and
algorithms. As a basic example, we simulate a Swap gate consisting of three
concatenated CNOT gates. Our work provides some pragmatic insights into the
prospects for building up to a fully scalable and fault-tolerant one-way
quantum computer with photons in realistic conditions.
