Experimental Cluster State Quantum Computation

Standard quantum computation is based on a universal set of unitary quantum logic gates which process qubits. In contrast to the standard quantum model, Raussendorf and Briegel proposed the one-way quantum computer, based on a highly-entangled cluster state, which is entirely different. We have experimentally realized four-qubit cluster states encoded into the polarization state of four photons. We fully characterize the quantum state by implementing the first experimental four-qubit quantum state tomography. Using this cluster state we demonstrate the feasibility of one-way quantum computing through a universal set of one- and two-qubit operations. Finally, our implementation of Grover's search algorithm demonstrates that one-way quantum computation is ideally suited for such tasks.