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Practical entanglement swapping with imperfect parametric down conversion sources and inaccurate detectors

Artur Scherer, Institute for Quantum Information Science at the University of Calgary in Alberta, Canada

(Session 5 : Friday from 5:00-7:00)

Abstract. Entanglement swapping between photon pairs is a fundamental building block in schemes using quantum relays and quantum memories to overcome the range limits of long distance quantum key distribution. Its practical realization, however, suffers from experimental deficiencies due to imperfect entangled-pairs parametric down conversion (PDC) sources and inaccurate detectors. We provide a model for practical entanglement swapping that takes into account the multi-pair nature of all PDC sources as well as detector inefficiencies and dark count events. In particular, we calculate the resultant mixed entangled quantum state given two imperfect PDC sources and the result of a Bell measurement with faulty detectors. We investigate how the entanglement present in the final state of the remaining modes is affected by the practical deficiencies. This allows us to suggest the implications of the imperfections on schemes using entanglement swapping as a fundamental tool. To test the predictions of our model, comparison with experiments on entanglement swapping is provided. We gratefully acknowledge the support of General Dynamics Canada, iCORE, CIFAR, MITACS, NSERC and Quantum Works in preparing this work.