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Wavelength-multiplexed quantum networks with ultrafast frequency combs


Highly entangled quantum networks (cluster states) lie at the heart of recent approaches to quantum computing1,2. Yet the current approach for constructing optical quantum networks does so one node at a time3,4,5, which lacks scalability. Here, we demonstrate the single-step fabrication of a multimode quantum resource from the parametric downconversion of femtosecond-frequency combs. Ultrafast pulse shaping6 is employed to characterize the comb's spectral entanglement7,8. Each of the 511 possible bipartitions among ten spectral regions is shown to be entangled; furthermore, an eigenmode decomposition reveals that eight independent quantum channels9 (qumodes) are subsumed within the comb. This multicolour entanglement imports the classical concept of wavelength-division multiplexing to the quantum domain by playing upon frequency entanglement to enhance the capacity of quantum-information processing. The quantum frequency comb is easily addressable, robust with respect to decoherence and scalable, which renders it a unique tool for quantum information.

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Figure 1: Experimental layout for the creation and characterization of multimode frequency combs.
Figure 2: Assessment of Duan inseparability criteria with ultrafast pulse shaping.
Figure 3: Frequency correlations of the quantum comb.
Figure 4: Amplitude spectra and corresponding squeezing values and quadratures for the leading six experimental supermodes retrieved from the covariance matrix.


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This work is supported by the French National Research Agency project Qualitime as well as the European Research Council starting grant Frecquam. C.F. is a member of the Institut Universitaire de France. J.R. acknowledges support from the European Commission through Marie Curie Actions.

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Authors and Affiliations



C.F. and N.T. developed and supervised the project. All authors designed the experiments. S.J. designed the optical cavity. J.R. and R.M.A. constructed the apparatus and performed the experiments. All authors contributed to the authorship of the manuscript.

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Correspondence to Nicolas Treps.

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The authors declare no competing financial interests.

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Roslund, J., de Araújo, R., Jiang, S. et al. Wavelength-multiplexed quantum networks with ultrafast frequency combs. Nature Photon 8, 109–112 (2014).

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