Summary

Quantum computation is a key emerging technology with the potential to revolutionize various core aspects of society, such as communication, medicine, or security, by exponentially surpassing its classical counterpart. Europe's strategic investments in fundamental research have recently enabled researchers to discover unique quantum states, promising for the practical realization of quantum computation, in novel hybrid nano-devices built by coupling small Superconducting Islands (SIs) to a semiconductor-based Quantum Dot (QD).

However, the fundamental physical properties of these novel systems are unknown in complex realistic scenarios involving multiple interconnected SIs and QDs and there is currently no proposal on how to exactly control them for quantum computation tasks. The project's objectives consist in filling these gaps in the state-of-the-art by providing the first theoretical predictions for the static properties of complex SI+QD systems and for their dynamical response to microwave pulses to be used then in constructing the optimal protocols for quantum computation.

The theoretical modelling of the complex strongly-correlated SI+QD systems will be enabled for the first time by accelerating the state-of-the-art quantum many-body models with a modern emulation technique inspired from nuclear physics, known as Eigenvector Continuation. As in nuclear physics, the latter is able to provide here a major advance in overcoming the computational barrier keeping the otherwise expensive but desirable microscopic models from interfacing directly with experimental data analysis and experimental design.

Upon achieving the above objectives, this project will not only increase our fundamental understanding of the basic building blocks of realistic quantum computing hardware, but will also provide new guidelines for their design, control and manipulation, bringing a significant contribution towards the practical realization of quantum computation.

Results

Scientific Report 2023

Scientific Report 2024

Publications

• Surrogate model solver for impurity-induced superconducting subgap states, Virgil V. Baran, Emil P. Frost, Jens Paaske, Phys. Rev. B 108, L220506 (2023), open access at arXiv:2307.11646.
• BCS surrogate models for floating superconductor-semiconductor hybrids, Virgil V. Baran, Jens Paaske, Phys. Rev. B, Phys. Rev. B 109, 224501 (2024), open access at arXiv:2402.18357.
• Spin-1 Haldane chains of superconductor-semiconductor hybrids, Virgil V. Baran, Jens Paaske, Phys. Rev. B 110, 064503 (2024) , open access at arXiv:2404.12207.
• Majorana modes in quantum dots coupled via a floating superconducting island, R. Seoane Souto, V. V. Baran, M. Nitsch, L. Maffi, J. Paaske, M. Leijnse, M. Burrello, Phys. Rev. B (submitted), open access at arXiv:2411.07068.
• The poor man’s Majorana tetron, M. Nitsch, L. Maffi, V. V. Baran, R. Seoane Souto, J. Paaske, M. Leijnse, M. Burrello, Phys. Rev. X (submitted), open access at arXiv:2411.11981.
• Yu-Shiba-Rusinov states in color superconducting quark matter, Virgil V. Baran, Jens Paaske, in preparation.
• Subspace learning of nonequilibrium steady states, Hans Christiansen, Virgil V. Baran, Jens Paaske, in preparation.

Conferences and workshops

• Spin-1 Haldane chains of super-semi hybrids, oral presentation at the "Workshop on Superconductor-Semiconductor Hybrids", March 12–14, 2024, Center for Quantum Device, Niels Bohr Institute, University of Copenhagen, Denmark.
• Spin-1 Haldane chains of super-semi hybrids, oral presentation at the "New Avenues in Quantum Materials – BalCon NAQM 2024" workshop, August 29–31, 2024, Chalmers University of Technology, Gothenburg, Sweden.