# FQXi Lecture Series on Quantum Foundations 22/23

During the next year, a series of visitors are coming to Siegen to discuss abour their views on quantum theory. These visits will be focused on philosophical and foundational questions, so we aim to have a relaxed environment where nonstandard or controversial ideas can be discussed at length.

To make this possible, instead of organising a conference, we will be hosting one visitor at a time, each staying for a few days. Apart from an introductory seminar, we will have a mostly free schedule for spontaneous discussions. Students and researchers from other fields are thus very welcome to join.

We will regularly update this page with the upcoming visitors and their intended topics.

This project if funded by the Foundational Questions Institute.

If you have any questions, send us an email.

# Upcoming Visits

TBA# Previous Visits

## Chris Fuchs (Quantum Mechanics Repainted in a QBist Style)

University of Massachusetts Boston

11th to 13th April 2023- Introductory lecture on the11th April, 10:00, room ENC-D 308.

- A second, more technical lecture is planned for the12th, 10:00, room ENC-D 120.

Abstract:QBism (pronounced like cubism) is a foundational program for quantum mechanics premised on the idea that quantum probabilities should be understood as Bayesian probabilities—that is, quantified degrees of belief or gambling attitudes. Philosophers hate it. “Wah, wah, wah, your quantum states are not real; they have to be because my philosophy says so!” What the philosophers have never appreciated (or perhaps cared about) is that this turn in thinking has motivated a significant number of theorems and constructions in quantum information science that might not have been discovered otherwise. In these two talks, I will sketch a sampling of those things, but also QBism’s most ambitious project yet: Rewriting the quantum formalism so that it wears its Bayesian character on its sleeve. By the end of the second lecture, we will see that it leads to a very deep mathematical question related to Hilbert’s still-unsolved 12th problem and suggests a novel quantum measurement that could have a number of uses in quantum information science.

## Nicolas Gisin (Indeterminism in Physics and Intuitionistic Mathematics)

Uni. of Geneva and Schaffhausen Institute of Technology

7th to 9th November 2022Introductory lecture on the 8th, 10am c.t., room ENC-D-308.

Abstract:Physics is formulated in terms of timeless axiomatic mathematics. However, time is essential in all our stories, in particular in physics. For example, to think of an event is to think of something in time. A formulation of physics based of intuitionism, a constructive form of mathematics built on time-evolving processes, offers a perspective that is closer to our experience of physical reality and may help bridging the gap between static relativity and quantum indeterminism. Historically, intuitionistic mathematics was introduced by Brouwer with a very subjectivist view where an idealized mathematician continuously produces new information by solving conjectures. Here, in contrast, I’ll introduce intuitionism as an objective mathematics that incorporates a dynamical/creative time and an open future. Standard mathematics appears as the view from the “end of time” and the usual real numbers appear as the hidden variables of classical physics.