Article

Experimental demonstration of a heralded entanglement source

Nature Photonics (Impact Factor: 29.96). 07/2010; 4(8). DOI: 10.1038/nphoton.2010.123
Source: arXiv

ABSTRACT The heralded generation of entangled states is a long-standing goal in
quantum information processing, because it is indispensable for a number of
quantum protocols. Polarization entangled photon pairs are usually generated
through spontaneous parametric down-conversion, but the emission is
probabilistic. Their applications are generally accompanied by post-selection
and destructive photon detection. Here, we report a source of entanglement
generated in an event-ready manner by conditioned detection of auxiliary
photons. This scheme benefits from the stable and robust properties of
spontaneous parametric down-conversion and requires only modest experimental
efforts. It is flexible and allows the preparation efficiency to be
significantly improved by using beamsplitters with different transmission
ratios. We have achieved a fidelity better than 87% and a state preparation
efficiency of 45% for the source. This could offer promise in essential
photonics-based quantum information tasks, and particularly in enabling optical
quantum computing by reducing dramatically the computational overhead.

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Available from: Andreas Reingruber, Aug 27, 2015
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    • "However, these experiments have much lower heralding efficiencies; to the best of our knowledge, the best reported heralding efficiency for these systems is 3.3 × 10 −9 , five orders of magnitude lower than what we measure here [43]. Experiments based on six-photon schemes resulted in two-photon states with a fidelity of 84% [39] and 87% [40]. The measured heralding efficiency of approximately 10 −2 (including coupling and detection losses) reported by the six-photon experiments is higher, but with the changes discussed above our measured heralding efficiency would approach or even surpass this value. "
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    • "Besides the remarkable progress of photon state engineering using atomic memories (Kimble (2008); Yuan et al. (2008)) the majority of current experiments is based on the production of photon pairs in the process of spontaneous parametric down-conversion (SPDC), where the entangled photon pair is concluded from post-selection of randomly occurring coincidences. Here we present new insights into the heralded generation of photon states (Barz et al. (2010); Wagenknecht et al. (2010)) that are maximally entangled in polarization (Schrödinger (1935)) with linear optics and standard photon detection from SPDC (Kwiat et al. (1995)). We utilize the down-conversion state corresponding to the generation of three pairs of photons, where the coincident detection of four auxiliary photons unambiguously heralds the successful preparation of the entangled state ( ´ Sliwa & Banaszek (2003)). "
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    • "In conclusion, we highlight a multi-photon experiment that generates heralded entangled states as required for long-distance quantum communication and scalable quantum computing. We note that during the course of the work presented here we learned of a parallel experiment by Wagenknecht et al.[31]. "
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    ABSTRACT: Entangled photons are a crucial resource for quantum communication and linear optical quantum computation. Unfortunately, the applicability of many photon-based schemes is limited due to the stochastic character of the photon sources. Therefore, a worldwide effort has focused in overcoming the limitation of probabilistic emission by generating two-photon entangled states conditioned on the detection of auxiliary photons. Here we present the first heralded generation of photon states that are maximally entangled in polarization with linear optics and standard photon detection from spontaneous parametric down-conversion. We utilize the down-conversion state corresponding to the generation of three photon pairs, where the coincident detection of four auxiliary photons unambiguously heralds the successful preparation of the entangled state. This controlled generation of entangled photon states is a significant step towards the applicability of a linear optics quantum network, in particular for entanglement swapping, quantum teleportation, quantum cryptography and scalable approaches towards photonics-based quantum computing.
    Nature Photonics 07/2010; 4(8). DOI:10.1038/nphoton.2010.156 · 29.96 Impact Factor
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