1. Institute for Experimental Physics, University of Vienna, Boltzmanngasse 5, A-1090 Vienna, Austria
2. Physics Department, Harvard University, Cambridge, Massachusetts 02138, USA
3. Institute for Quantum Optics and Quantum Information (IQOQI), Austrian Academy of Sciences, Boltzmanngasse 3, A-1090 Vienna, Austria
4. Present address: Max-Planck-Institut für Quantenoptik und Sektion Physik der Ludwig-Maximilians-Universität, Schellingstr. 4, 80799 München, Germany.

Correspondence to: Robert Prevedel¹Anton Zeilinger^1,3 Correspondence and requests for materials should be addressed to R.P. (Email: robert.prevedel@univie.ac.at) or A.Z. (Email: zeilinger-office@quantum.at).

As information carriers in quantum computing¹, photonic qubits have the advantage of undergoing negligible decoherence. However, the absence of any significant photon–photon interaction is problematic for the realization of non-trivial two-qubit gates. One solution is to introduce an effective nonlinearity by measurements resulting in probabilistic gate operations^{2, 3}. In one-way quantum computation^{4, 5, 6, 7, 8}, the random quantum measurement error can be overcome by applying a feed-forward 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 one-way quantum computation is based) is prepared. Here we realize a concatenated scheme of measurement and active feed-forward in a one-way 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 feed-forward components function with very high speed and low error for detected photons. With present technology, the individual computational step (in our case the individual feed-forward cycle) can be operated in less than 150 ns using electro-optical modulators. This is an important result for the future development of one-way quantum computers, whose large-scale implementation will depend on advances in the production and detection of the required highly entangled cluster states.

MORE ARTICLES LIKE THIS

These links to content published by NPG are automatically generated.