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Abstract
We report the characterization of a universal set of logic gates for oneway quantum computing using a fourphoton '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 controlledNOT, 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 characterization 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 faulttolerant oneway quantum computer with photons in realistic conditions.
Original language  English 

Article number  053030 
Journal  New Journal of Physics 
Volume  15 
DOIs  
Publication status  Published  May 2013 
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Projects
 1 Finished

MICROSTRUCTURED FIBRE FOR QUANTUM INFORMATION
Engineering and Physical Sciences Research Council
1/10/07 → 30/09/10
Project: Research council