Oneway quantum computer

The oneway or measurement based quantum computer is a method of quantum computing that first prepares an entangled resource state, usually a cluster state or graph state, then performs single qubit measurements on it. It is "oneway" because the resource state is destroyed by the measurements.
The outcome of each individual measurement is random, but they are related in such a way that the computation always succeeds. In general the choices of basis for later measurements need to depend on the results of earlier measurements, and hence the measurements cannot all be performed at the same time.
Equivalence to quantum circuit model
Any oneway computation can be made into a quantum circuit by using quantum gates to prepare the resource state. For cluster and graph resource states, this requires only one twoqubit gate per bond, so is efficient.
Conversely, any quantum circuit can be simulated by a oneway computer using a twodimensional cluster state as the resource state, by laying out the circuit diagram on the cluster; Z measurements ( basis) remove physical qubits from the cluster, while measurements in the XY plane ( basis) teleport the logical qubits along the "wires" and perform the required quantum gates.^{[1]} This is also polynomially efficient, as the required size of cluster scales as the size of the circuit (qubits x timesteps), while the number of measurement timesteps scales as the number of circuit timesteps.
Implementations
Oneway quantum computation has been demonstrated by running the 2 qubit Grover's algorithm on a 2x2 cluster state of photons.^{[2]}^{[3]} A linear optics quantum computer based on oneway computation has been proposed.^{[4]}
Cluster states have also been created in optical lattices,^{[5]} but were not used for computation as the atom qubits were too close together to measure individually.
References
 ^ R. Raussendorf, D. E. Browne, and H. J. Briegel (2003). "Measurement based Quantum Computation on Cluster States". Phys. Rev. A 68 (2): 022312. arXiv:quantph/0301052. doi:10.1103/PhysRevA.68.022312.
 ^ P. Walther, K. J. Resch, T. Rudolph, E. Schenck, H. Weinfurter, V. Vedral, M. Aspelmeyer and A. Zeilinger (2005). "Experimental oneway quantum computing". Nature 434 (7030): 169. doi:10.1038/nature03347. PMID 15758991. http://www.nature.com/nature/journal/v434/n7030/full/nature03347.html.
 ^ Robert Prevedel, Philip Walther, Felix Tiefenbacher, Pascal Böhi, Rainer Kaltenbaek, Thomas Jennewein and Anton Zeilinger (2007). "Highspeed linear optics quantum computing using active feedforward". Nature 445 (7123): 65–69. doi:10.1038/nature05346. PMID 17203057. http://www.nature.com/nature/journal/v445/n7123/full/nature05346.html.
 ^ Daniel E. Browne, Terry Rudolph (2005). "Resourceefficient linear optical quantum computation". Physical Review Letters 95 (1): 010501. arXiv:quantph/0405157. Bibcode 2005PhRvL..95a0501B. doi:10.1103/PhysRevLett.95.010501. PMID 16090595.
 ^ Olaf Mandel, Markus Greiner, Artur Widera, Tim Rom, Theodor W. Hänsch and Immanuel Bloch (2003). "Controlled collisions for multiparticle entanglement of optically trapped atoms". Nature 425 (6961): 937. doi:10.1038/nature02008. PMID 14586463. http://www.nature.com/nature/journal/v425/n6961/full/nature02008.html.
 R. Raussendorf and H. J. Briegel (2001). "A OneWay Quantum Computer". Physical Review Letters 86 (22): 5188. Bibcode 2001PhRvL..86.5188R. doi:10.1103/PhysRevLett.86.5188. PMID 11384453.
 D. Gross, J. Eisert, N. Schuch, D. PerezGarcia (2007). "Measurementbased quantum computation beyond the oneway model". Physical Review A 76 (5): 052315. arXiv:0706.3401. doi:10.1103/PhysRevA.76.052315. Noncluster resource states
 A. Trisetyarso and R. Van Meter (2010). "Circuit Design for A MeasurementBased Quantum CarryLookahead Adder". International Journal of Quantum Information 8 (05): 843. arXiv:0903.0748. doi:10.1142/S0219749910006496. Measurementbased quantum computation, quantum carrylookahead adder
Quantum information science General Quantum communication Quantum capacity • Quantum channel • Quantum cryptography (Quantum key distribution) • Quantum teleportation • Superdense coding • LOCC • Entanglement distillationQuantum algorithms Universal quantum simulator • Deutsch–Jozsa algorithm • Grover's search • quantum Fourier transform • Shor's factorization • Simon's Algorithm • Quantum phase estimation algorithm • Quantum annealingQuantum complexity theory Quantum computing models Quantum circuit (Quantum gate) • Oneway quantum computer (cluster state) • Adiabatic quantum computation • Topological quantum computerDecoherence prevention Quantum error correction • Stabilizer codes • EntanglementAssisted Quantum Error Correction • Quantum convolutional codesPhysical implementationsQuantum optics Ultracold atoms Spinbased Superconducting quantum computing Charge qubit • Flux qubit • Phase qubitCategories:
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