Xanthe Croot joined EQuS (the 2011–2017 iteration of EQUS) as a PhD student in 2014, working with Chief Investigator David Reilly at USYD on semiconducting quantum computing. After completing her PhD in 2018, she received a Dicke Fellowship to Princeton University, where she worked with Professor Jason Petta on hybrid semisuperconducting experiments, and with Professor Andrew Houck on protected superconducting qubits. Xanthe returned to Australia as a Lecturer in Quantum Science at USYD in November 2022, and rejoined EQUS as a Chief Investigator on 1 July 2023.

Xanthe Croot Xanthe’s group’s research fits within EQUS’ Designer Quantum Materials and 1kQubit Flagship research programs.
Xanthe was also successful on two ARC grants in 2023: a LIEF grant and a DECRA on demonstrations of single protected qubits. This work will complement another aspect of her EQUS research—to develop a roadmap for coupling and scaling protected qubits, beyond the initial demonstrations of protection.

“Superconducting circuits are among the most successful platforms for realising large-scale coherent quantum systems, exemplified by industrial implementations of quantum processors at Google and IBM. A leading candidate for industrial superconducting quantum computing efforts is a type of qubit known as a transmon qubit. However, the transmon is inherently sensitive to depolarisation processes which limit qubit performance.

“The fluxonium qubit is steadily gaining traction as a viable competitor to the transmon qubit. For the cost of one additional circuit element (an inductor) and an external control knob (a magnetic field), the fluxonium is insensitive to sources of noise that affect other qubits, is highly anharmonic (enabling fast gates with suppressed leakage), and has millisecond coherence times. My group will tackle some of its biggest outstanding challenges, including how we can further reduce fluxonium error rates and do better two-qubit gates.

“As a new Chief Investigator, I’m really looking forward to being part of a diverse community of researchers working on harnessing the beauty of quantum mechanics and translating it into realworld applications, like quantum computing. I’m looking forward to developing collaborations in the broader EQUS network, to strengthen and enrich my own research and inspire new and creative lines of investigation.” Xanthe Croot

Published in the 2023 EQUS Annual Report