School Seminar Program

Connecting up the quantum internet: building quantum interconnects using rare earth crystals

Dr Rose Ahlefeldt
Department of Quantum Science and Technology, RSPhys, ANU

The future quantum internet is likely to be heterogeneous: different components, such as quantum computers, quantum repeaters, and quantum sensors, will be based on different physical systems. Quantum interconnects are needed to connect these devices to the network and to each other. Rare earth crystals are a versatile platform for quantum interconnects, able to translate quantum information between spins, microwave photons and optical photons. In this seminar, I will focus on one type of interconnect, a singlephoton microwave to optical frequency converter, which could connect superconducting and spin quantum computers to the quantum internet.

The converter we are developing will use the magnetically ordered crystal ErLiF4, and achieves conversion via the nonlinearity arising from operating close to microwave and optical resonances of the Er ions. The high Er concentration gives the strong coupling required for high efficiency conversion, but also places the crystals in an interesting regime: the interactions between ions give rise to collective excitations, while the strong coupling to light means the atomic resonances substantially modify the propagation of light in the crystal, perhaps even leading to negative refraction. I will discuss our recent optical studies of these crystals and their promise both for frequency conversion and for studying exotic optical phenomena.


Rose Ahlefeldt completed her PhD at ANU in 2013, studying europium crystals as a platform for quantum computing. She then worked as a postdoc at Laboratoire Aimé Cotton, France as well as at Montana State University, USA on a Fulbright Scholarship, before returning to Australia in 2016 as an Australian Research Council DECRA fellow. In 2018 she was named ACT Scientist of the Year for her research on quantum memory hardware. Her research focuses in two main areas: studying interactions in rare earth crystals through theoretical models and highresolution optical spectroscopy, and optimising rare earth crystals for use in quantum information, including as quantum memories, quantum processors and optical quantum interconnects.

Join the Zoom Meeting
Meeting ID: 941 1170 1666
Password: 664 425

Updated:  7 October 2022/ Responsible Officer:  Director, RSPhys/ Page Contact:  Physics Webmaster