Quantum Optics Seminar: Rose Ahlefeldt

Quantum technology with rare earth crystals

Rare earth ions in crystals are characterised by optical transitions in the near-IR and visible spectrum with narrow linewidths and very long coherence times. In addition, most rare earths possess spin transitions, also with extremely long coherence time. This combination of optical and spin properties makes rare earth materials a flexible platform for quantum information applications, such as quantum memories, quantum light sources, quantum processors and quantum interconnects.

 In this talk, I will describe work in Australia to build rare-earth based quantum technologies, with a particular focus on quantum memories and quantum interconnects using erbium-based crystals. Erbium offers an optical transition in the telecom C-band of optical fibre, making it well suited to short and long-distance quantum communications applications. For quantum memories, dilute Er doped into Y₂SiO₅ is used, and I will discuss recent experiments which showed spin spate quantum storage with an efficiency of 74%, and storage of multiple temporal modes. For quantum interconnects, we are investigating single-photon microwave-optical frequency conversion via an off-resonant three wave mixing process. This application requires an extremely strong atom light interaction, for which ErLiF₄ is a good candidate.  I will describe our work to characterise the optical properties of this strongly interacting material, and the effect they have on the frequency conversion process.