Tuesday, August 2, 2011

Experimental high-dimensional two-photon entanglement and violations of generalized Bell inequalities

    • Adetunmise C. Dada, Jonathan Leach, Gerald S. Buller, Miles J. Padgett & Erika Andersson
Quantum entanglement1, 2 plays a vital role in many quantum-information and communication tasks3. Entangled states of higher-dimensional systems are of great interest owing to the extended possibilities they provide. For example, they enable the realization of new types of quantum information scheme that can offer higher-information-density coding and greater resilience to errors than can be achieved with entangled two-dimensional systems (see ref. 4 and references therein). Closing the detection loophole in Bell test experiments is also more experimentally feasible when higher-dimensional entangled systems are used5. We have measured previously untested correlations between two photons to experimentally demonstrate high-dimensional entangled states. We obtain violations of Bell-type inequalities generalized to d-dimensional systems6 up to d=12. Furthermore, the violations are strong enough to indicate genuine 11-dimensional entanglement. Our experiments use photons entangled in orbital angular momentum7, generated through spontaneous parametric down-conversion8, 9, and manipulated using computer-controlled holograms.

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