At the Institute of Photonic Sciences (ICFO), the QIA Team of the Quantum Photonics with Solids and Atoms group of Prof. Hugues de Riedmatten is working towards a functional quantum repeater link to enable a European-wide quantum network. Our quantum network nodes are based on rare-earth-doped solid-state memories and narrowband non-degenerate photon pair sources. One photon of the source is resonant with the quantum memory, and the other is at telecom wavelengths and can be sent over long distances in an optical fiber. The quantum memory is based on the atomic frequency comb scheme, where the dopant atoms are prepared with laser pulses in a comb structure. An incoming photon will be collectively absorbed by the atoms and thus stored in the collective state of the atoms. After several microseconds set by the structure of the comb, the photon will be re-emitted. For long-term storage, we apply additional laser pulses on the atoms prior to the reemission process and transfer the atoms into a long-lived groundstate.

The medium term goal of our project is to bring quantum memory nodes outside the labs to perform experiments in the installed fiber network. To make that goal feasible, the nodes need to be transportable and need to work as autonomously as possible. The goal of this internship is to make first steps towards a rack-integrated quantum repeater node, by designing, building and demonstrating a rack-integrated memory compatible photon pair source.