Tenure
November 9 – December 1, 2019
Philipp Höhn
Research Fellow, University College London
Philipp Höhn is a research fellow (‘It-from-Qubit’-Fellow) at University College London, U.K. After completing his Ph.D. at Universiteit Utrecht in the Netherlands, he has been a postdoc at the Perimeter Institute in Canada and the Institute for Quantum Optics and Quantum Information in Vienna, Austria, before moving to London. His research is motivated by general questions in and around quantum gravity and includes wide-ranging topics in classical gravity, quantum information, the foundations of physics, and mathematical physics. His endeavors thereby frequently touch on foundational questions that are also of philosophical interest.
One focus of his explorations has been on the relational paradigm of dynamics to address the notorious problem of time in quantum gravity. In this context, he has worked on better understanding observable and dynamical properties in gravitational theories and on developing a notion of quantum general covariance based on quantum reference frames. He has also produced a reconstruction of quantum theory from informational principles in order to provide one possible answer to Wheeler’s “how come the quantum?” Currently, he is interested in the interplay between quantum correlations and spacetime geometry and in the emergence of classicality from within quantum theory, specifically in the presence of chaos.
Thursday, November 14, 2019
4:00-5:00 pm
Wilder Hall, Room 202, Dartmouth College
Events
Quantum Seminar: Quantum General Covariance and the Problem of Time
Reference frames provide the vantage points from which to describe the remaining physics. General covariance essentially posits that “all the laws of physics are the same in every reference frame.” While this is an established pillar of general relativity and usually interpreted in terms of coordinate invariance, its fate in the quantum realm remains an open question. This is a challenge because treating frames fundamentally as quantum systems themselves is inevitable in quantum gravity, where coordinates are a priori unavailable, but also in quantum foundations once accepting that all frames are physical systems. Both fields thus face the question of how to describe physics from the perspective of quantum frames and how the descriptions relative to different such choices are related. Philipp Höhn summarizes a recent “perspective-neutral” approach to such quantum frame perspective changes, which works in analogy to coordinate changes on a manifold, except that these “quantum coordinate changes” proceed between different Hilbert spaces. He then focuses on temporal reference frames, i.e., quantum clocks, and uses this approach to argue for a new perspective on the infamous problem of time in quantum gravity and the “wave function of the universe.”
