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Conditional control of the quantum states of remote atomic memories for quantum networking

Abstract

Quantum networks hold the promise for revolutionary advances in information processing with quantum resources distributed over remote locations via quantum-repeater architectures. Quantum networks are composed of nodes for storing and processing quantum states, and of channels for transmitting states between them. The scalability of such networks relies critically on the ability to carry out conditional operations on states stored in separated quantum memories. Here, we report the first implementation of such conditional control of two atomic memories, located in distinct apparatuses, which results in a 28-fold increase of the probability of simultaneously obtaining a pair of single photons, relative to the case without conditional control. As a first application, we demonstrate a high degree of indistinguishability for remotely generated single photons by the observation of destructive interference of their wave packets. Our results demonstrate experimentally a basic principle for enabling scalable quantum networks, with applications also to linear optics quantum computation.

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Figure 1: Overview of the experiment.
Figure 2: Probabilities p11 and p1122 of coincidence detection as functions of the number N of trials waited between the independent preparation of the two ensembles (L, R) with one excitation each.
Figure 3: Conditional joint-detection probability p22c(τ) of recording events in both D2a and D2b, once the two ensembles are ready to fire, as a function of the time difference τ between the two detections.
Figure 4: Probability densities pd for the wave packets of fields 2L and 2R derived from the distribution of detection events over time td.

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Acknowledgements

This research is supported by the Disruptive Technologies Office (DTO) and by the National Science Foundation. J.L. acknowledges financial support from the European Union (Marie Curie fellowship). D.F. acknowledges financial support by CNPq (Brazilian agency).

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Correspondence to H. J. Kimble.

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Felinto, D., Chou, C., Laurat, J. et al. Conditional control of the quantum states of remote atomic memories for quantum networking. Nature Phys 2, 844–848 (2006). https://doi.org/10.1038/nphys450

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