Recent developments have recognized that quantum causal structures introduce a new non-classical resource known as causal indefiniteness, opening up novel perspectives in quantum information. Despite theoretical advancements and several experimental realizations, the conceptual implications of indefinite causality remain poorly understood. Concurrently, quantum causality has emerged as a crucial foundation for elucidating the discrepancies between operational approaches and spacetime physics. It has already facilitated a novel or enhanced understanding of fundamental concepts such as events (Vilasini and Renner, Phys. Rev. Lett. 133, 080201), facts (Brukner, Nature Phys. 16, 1172–1174, 2020), inputs/outputs (Chiribella and Liu, Comm. Phys. 5, 190, 2022), systems (Grinbaum, Stud. Hist. Phil. Mod. Phys. 58, 22-30, 2017), and computation (Araujo et al., Phys. Rev. A 96, 052315, 2017).
In this PhD project, the candidate will develop a systematic understanding of the conceptual lessons of indefinite causality within the classical, quantum, and generalized probabilistic theory (GPT) frameworks. They will examine the foundational significance of bipartite and multipartite settings, including their spatiotemporal and computational capacities. To make significant progress in quantum foundations, the candidate will seek to extract insights from indefinite causality to deepen our understanding of standard quantum theory, quantum information, and quantum interpretations.
Specific research questions include:
• Establishing conceptual grounds for the identification of systems and events across time, particularly in relation to indefinite causal orders and to "Wigner's friend" scenarios.
• Placing this emerging foundational discussion within a broader philosophical and metaphysical framework.
• Addressing the notion of the agent/observer as a theoretical rather than a metatheoretical entity.
Publications are expected in physics journals (PRL, PRA, NJP, Quantum) and/or philosophy of physics journals (Philosophy of physics, BJPS, Found. Phys., SHPMP). Collaborations are expected with groups in France, Austria, Belgium, and Canada.