Dr. Viktoria Kabel, Quantum Information Theory Group at ITP, ETH Zürich
In this talk, we will explore the interface between quantum theory and gravity through two lenses.
The first lens is the study of indefinite causal order. While, classically, the causal order between two events is fixed – either event A happens before event B or vice versa – this is no longer true in quantum theory. There, we can encounter superpositions of causal orders, which could be realised, for example, by sending particles along a superposition of different paths in an optical experiment or, hypothetically, by creating a superposition of gravitational fields that directly affects spacetime and the corresponding causal structure.
The second lens is the study of quantum reference frames. This approach takes into account the quantum properties of the reference frames that we use, explicitly or implicitly, in our description of physical systems. As a result, quantum features like superposition or entanglement become frame-dependent. When applied to scenarios with a superposition of causal orders, these insights help connect the seemingly disparate proposal for realising indefinite causal order, shedding a little light on the puzzling concept of spacetimes in superposition along the way.
Article
https://arxiv.org/abs/2211.15685v2
Recording
The talk will be streamed, however there will be no recording.