Abstract-Wavelength-multiplexed quantum networks with ultrafast frequency combs

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  Experimental layout for the creation and characterization of multimode frequency combs
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  Jonathan Roslund,
• Renné Medeiros de Araújo,
• Shifeng Jiang,
• Claude Fabre
• & Nicolas Treps

http://www.nature.com/nphoton/journal/vaop/ncurrent/full/nphoton.2013.340.html

Highly entangled quantum networks (cluster states) lie at the heart of recent approaches to quantum computing^1, 2. Yet the current approach for constructing optical quantum networks does so one node at a time^3, 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 entanglement^7, 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.