Quantum computers promise to efficiently solve certain tasks and problems beyond the reach of classical computers by harnessing purely quantum properties. One such approach is bosonic quantum computing, which encodes information into bosonic modes such as photonic modes, exploiting their infinite-dimensional state space rather than just relying on two-level systems.

During her Ph.D. studies, Josefine Bjørndal Robl explored how bosonic quantum computing can be used for both near term applications and quantum error correction. Her main research focused on a specialised quantum computation called Gaussian boson sampling, which is deeply connected to graph theory. Leveraging this connection, she developed a sampling-based algorithm to identify clusters within data and argued for the possibility of this algorithm being faster than its classical counterpart.

Her work also explored how quantum information stored in bosonic systems can be protected from errors using specialised quantum codes, focusing on a code that combines the continuous variable error correction capabilities of a bosonic code with the global information encoding of a topological code.

The Ph.D. study was completed at Department of Physics and Astronomy, Faculty of Natural Sciences, Aarhus University.

This summary was prepared by the Ph.D. student.

Time: Thursday the 6th of November 2025 at 13:00.
Place: Building 1525, room 626, Det Skæve Rum, Department of Physics and Astronomy, Aarhus University, Ny Munkegade 120, 8000 Aarhus C.
Title of PhD thesis: Explorations in Bosonic Quantum Computing – A Study on Applications and Improvements of Quantum Algorithms.
Contact information: Josefine Bjørndal Robl, e-mail: robl@phys.au.dk, tel.: +45 24441149.
Members of the assessment committee:
Senior Researcher Mikkel Heuck, Department of Electrical and Photonics Engineering, Technical University of Denmark, Denmark.
Professor Lucia Caspani, Dipartimento di Scienza e Alta Tecnologia, Insubria University, Italy.
Associate Professor Jan Arlt (chair), Department of Physics and Astronomy, Aarhus University, Denmark.
Main supervisor: Professor Nikolaj Thomas Zinner, Department of Physics and Astronomy, Aarhus University, Denmark.
Co-supervisor: Head of Research Janus Halleløv Wesenberg, Kvantify ApS, Denmark.
Language: The Ph.D. dissertation will be defended in English.

The defence is public.
The Ph.D. thesis is available for reading at the Graduate School of Natural Sciences/GSNS, Ny Munkegade 120, building 1521, 8000 Aarhus C