Photon frequency convertor for quantum networks

Quantum network consisting of separate nodes processing information and linked by quantum channels is a promising and widely investigated general architecture for scalable and distributed quantum computing [1]. The most feasible proposals for realisation of such a network involve matter-based nodes (e.g. trapped atoms or ions or solid-state systems) communicating by photons [2]. This approach combines advantages of long-living and precisely manipulated systems for nodes with fast and convenient for long distance information transfer ones. Implementation of such a scheme opens up a lot of research challenges where establishing a reliable channel for quantum state transfer between two nodes by photons is essential, once the nodes are operating. It would by particularly convenient to have a standard channel that can different systems be talking to and the telecom band photons are good candidates for that because of well-established optical fiber infrastructure. In our work we implement a single photon frequency conversion to telecom band so that quantum systems with different emitting frequencies could be used in such a network. This approach also permits to minimize the losses and increase distances to 10s-kilometre range by exploiting the lowest attenuation band in fibers. The work is aimed in particular on developing device capable of converting photons produced by P
^3/2
-D
^5/2
transition in
⁴⁰
Ca+ ion that corresponds to 854.2 nm wavelength as a promising candidate for the network nod.