30 May 2013 A Photon Pair Source for Quantum Repeaters

Cavity enhanced down conversion source

Physics highlights the demonstration of a novel quantum light source for solid state quantum memories by ICFO researchers. ICFO researchers demonstrate a novel quantum light source capable of connecting solid state quantum memories emitting in the visible to the optical fiber network. The source is ideally suited for long distance quantum information networks. The study has been published in Physical Review Letters and selected as viewpoint in Physics. The research team includes former Icfonian Dr Julia Fekete, now at the University of Ottago in New Zealand, ICFO PhD student Daniel Rieländer and ICFO research fellow Dr Matteo Cristiani. The group is led by ICREA Prof. Hugues de Riedmatten, leader at ICFO of the Quantum photonics with solids and atoms group.

Quantum memories are important devices in quantum information science, in particular for the development of long distance quantum communication using quantum repeaters. Praseodymium doped crystals are currently one of the most promising solid state quantum memories, potentially enabling efficient and long lived quantum light storage. However, they have two major drawbacks: they absorb light at a wavelength of 606 nm where the loss in optical fibers is very high and they feature a narrow spectral bandwidth limited to a few MHz which has prevented so far the realization of a suitable quantum light source. To overcome these limitations, the authors used a novel type of quantum light source based on widely non degenerate cavity enhanced spontaneous down conversion. The source creates ultra-narrowband photon pairs with one photon compatible with the solid state quantum memory and the other one at a telecommunication wavelength, thus allowing the connection between the quantum memory and the optical fiber network.