Leader : Tanzilli Sébastien
External Collaborators : Rarity J. (Department of Electrical & Electronic Engineering, University of Bristol), Wadsworth W. (Centre for Photonics and Photonic Materials, University of Bath)
Quantum communication potential lies in performing operations (teleportation, entanglement swapping, quantum logic gates) that have no classical analogues. Photon coalescence, or Hong-Ou-Mandel (HOM) interference, lies at the very heart of all these quantum operations. In such a situation, two identical, say indistinguishable, photons enter a 50/50 beam-splitter (BS) simultaneously through different input ports, and actually “stick” together for exiting through the same output port of the device. This destructive interference regarding the cases where the two photons exit through different outputs is purely quantum. If this effect is commonly observed with photons emitted by the same source, experiments involving truly independent photons still represent a major challenge. Similarly, employing photons created using different emission processes remains to be demonstrated for enabling quantum communication networks.
In this scope, the LPMC masters the technologies for manufacturing integrated waveguides on periodically poled lithium niobate (PPLN/W), which currently represent the most efficient photon-pair sources. On the other hand, we have recently initiated a very active collaboration with the group of Prof. John Rarity at the University of Bristol (UK), where photon-pair sources based on photonic crystal fibers (PCF) are developed in a partnership with the University of Bath. Our aim is to merge these two types of structures (PCF and PPLN/W) within a single setup so as to observe HOM interference.
Such an interference has recently been obtained using photons coming not only from independent sources (pumped by independent lasers in the near future), but also created using different nonlinear processes, i.e., mixing three or four waves for the PPLN/W and the PCF, respectively . This opens the way towards achieving actual quantum network applications, to which any user can get connected, independently of the employed photonic quantum technology. Here the only key feature is to emit photons having appropriate spectral characteristics.
The next steps for this project are to generate entangled photons with these two independent sources, and to realize an entanglement teleportation experiment.
 "Two-photon interference between disparate sources for quantum networking", A. R. McMillan, L. Labonté, A. S. Clark, B. Bell, O. Alibart, A. Martin, W. J. Wadsworth, ST, and J. G. Rarity, Sci. Rep. 3, 2032 (2013).
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