Highspeed linear optics quantum computing using active feedforward
Abstract
As information carriers in quantum computing, photonic qubits have the advantage of undergoing negligible decoherence. However, the absence of any significant photonphoton interaction is problematic for the realization of nontrivial twoqubit gates. One solution is to introduce an effective nonlinearity by measurements resulting in probabilistic gate operations. In oneway quantum computation, the random quantum measurement error can be overcome by applying a feedforward technique, such that the future measurement basis depends on earlier measurement results. This technique is crucial for achieving deterministic quantum computation once a cluster state (the highly entangled multiparticle state on which oneway quantum computation is based) is prepared. Here we realize a concatenated scheme of measurement and active feedforward in a oneway quantum computing experiment. We demonstrate that, for a perfect cluster state and no photon loss, our quantum computation scheme would operate with good fidelity and that our feedforward components function with very high speed and low error for detected photons. With present technology, the individual computational step (in our case the individual feedforward cycle) can be operated in less than 150ns using electrooptical modulators. This is an important result for the future development of oneway quantum computers, whose largescale implementation will depend on advances in the production and detection of the required highly entangled cluster states.
 Publication:

Nature
 Pub Date:
 January 2007
 DOI:
 10.1038/nature05346
 arXiv:
 arXiv:quantph/0701017
 Bibcode:
 2007Natur.445...65P
 Keywords:

 Quantum Physics
 EPrint:
 19 pages, 4 figures