Post-Doctoral Research Visit F/M Quantum causality in symmetry-constrained systems

The Inria Saclay-Île-de-France Research Centre was established in 2008. It has developed as part of the Saclay site in partnership with Paris-Saclay University and with the Institut Polytechnique de Paris .

The centre has 40 project teams , 27 of which operate jointly with Paris-Saclay University and the Institut Polytechnique de Paris; Its activities occupy over 600 people, scientists and research and innovation support staff, including 44 different nationalities.

Context

Every year Inria International Relations Department has a few postdoctoral positions in order to support Inria international collaborations.

The postdoctoral contract will have a duration of 24 months. The default start date is November 1st, 2026 and not later than January 1st 2027. The postdoctoral fellow will be recruited by one of the Inria Centres in France but it is recommended that the time is shared between France and the partner’s country (please note that the postdoctoral fellow has to start his/her contract being in France and that the visits have to respect Inria rules for missions.)

Scientific Context

When studying experiments involving quantum systems, questions about cause and effect cannot be answered with standard classical causality frameworks. This limitation was first revealed by Bell’s theorem, a result that challenges our classical notions of causality and has applications in quantum cryptography, as well as in efforts to understand the computational advantage that quantum theory has over classical theory. This fact has motivated the development, over the past decade, of frameworks to study quantum causality. Such frameworks are not only steps towards a foundational understanding of quantum theory, but also have applications to quantum computing architectures. Recent work shows that the study of the internal causal structure of unitary transformations requires extending the standard model of quantum circuits. This led to the idea of generalized partitions [1], where to combine subsystems one moves beyond purely tensor-product composition to a framework that incorporates both tensor products and direct sums.

Meanwhile, a different research direction also pushes us towards a composition rule that involves direct sums apart from tensor products: the study of physical systems subject to symmetry constraints, such as fermionic systems. Learning the fundamental properties of such systems (for example, that one cannot reconstruct a bipartite state from the results of local measurements [2]) has both foundational and practical interest, since such symmetry constraints model the lack of a shared reference frame between parties, which can impact tasks such as communication and cryptography.

Mission

The convergence in the composition rules arising from those two research directions hints at a deeper connection between them. As such, the objective of this project is to carry forward the existing collaboration between Inria project-teams Quriosity and Quacs and Prof. Robert Spekkens (University of Waterloo and Perimeter Institute) to investigate quantum causal structure in the presence of symmetries.

The project has two main goals:

• Use generalized partitions (or a further expansion of that framework) to model and understand causality in symmetry-constrained systems.
• Leverage insights from symmetry-constrained systems to address open questions in quantum causality. For example, the fact that many times a symmetry can be understood as arising from a lack of shared reference frame shows that it hides a deeper theory where apparent puzzles dissolve; we can investigate whether a similar phenomenon also happens with generalized partitions.

More broadly, this study will clarify how causal modelling differs between standard quantum theory and symmetry-constrained quantum theory. In the future these insights may also guide the development of causal frameworks for other conceivable physical theories (generalized probabilistic theories), helping to further isolate what is conceptually unique about quantum theory. Therefore, while grounded in concrete research directions, this project naturally opens the door to broader follow-up questions.

[1] Augustin Vanrietvelde, Octave Mestoudjian, and Pablo Arrighi, “Partitions in quantum theory”, arXiv: 2506.22218.

[2] Daniel Centeno, Marco Erba, Thomas D. Galley, David Schmid, John H. Selby, Robert W. Spekkens, Sina Soltani, Jacopo Surace, Alex Wilce, and Yìlè Yīng, “Symmetry-induced failures of tomographic locality: Constructing foil theories by twirling”, Phys. Rev. A 112, L030202 (2025).

Main Activities

• Carry out research on theoretical quantum information, quantum causality, and quantum foundations (publications of research articles, participation in conferences)
• Lead the collaboration between Inria Saclay and the University of Waterloo on quantum causality (organization of seminars and research visits)
• Supervise research internships

Candidates for postdoctoral positions are recruited after the completion of their Ph.D. or a first postdoctoral period. To be eligible, candidates must have defended their Ph.D. no more than 3 years before the start date of the contract. As the start date will be between November 1, 2026 and January 1, 2027, the latest eligible Ph.D. defense date will vary accordingly (approximately between November 1, 2023 and January 1, 2024).

In order to encourage mobility, the postdoctoral position must take place in a scientific environment that is truly different from the one of the Ph.D. (and, if applicable, from the position held since the Ph.D.); particular attention is thus paid to French or international candidates who obtained their doctorate abroad.

Skills

• PhD degree in computer science, physics, or a related field
• Proficiency in the fields of quantum information and causal modelling

Instruction to apply

In addition to the (mandatory) online application on the Inria website, the candidate should express their interest by contacting Augustin Vanrietvelde (vanrietvelde@telecom-paris.fr) via email.

Deadline for application: June 7, 2026

• Subsidized meals
• Partial reimbursement of public transport costs
• Leave: 7 weeks of annual leave + 10 extra days off due to RTT (statutory reduction in working hours) + possibility of exceptional leave (sick children, moving home, etc.)
• Possibility of teleworking (after 6 months of employment) and flexible organization of working hours
• Professional equipment available (videoconferencing, loan of computer equipment, etc.)
• Social, cultural and sports events and activities
• Access to vocational training
• Social security coverage

Monthly gross salary : 2 788 euros/month