Qiss

Pablo Arrighi
University of Paris-Saclay

Quantum networks theory

Abstract:
The formalism of quantum theory over discrete systems is extended in two significant ways. First, tensors and traceouts are generalized, so that systems can be partitioned according to almost arbitrary logical predicates. Second, quantum evolutions are generalized to act over network configurations, in such a way that nodes be allowed to merge, split and reconnect coherently in a superposition. The hereby presented mathematical framework is anchored on solid grounds through numerous lemmas. Indeed, one might have feared that the familiar interrelations between the notions of unitarity, complete positivity, trace-preservation, non-signalling causality, locality and localizability that are standard in quantum theory be jeopardized as the partitioning of systems becomes both logical and dynamical. Such interrelations in fact carry through.
(Joint work with Amélia Durbec and Matt Wilson, reference: https://arxiv.org/abs/2110.10587

David Wallace
Pittsburg University

Quantum gravity at low energies

I provide a conceptually-focused presentation of `low-energy quantum gravity’ (LEQG), the effective quantum field theory obtained from general relativity and which provides a well-defined theory of quantum gravity at energies well below the Planck scale. I emphasize the extent to which some such theory is required by the abundant observational evidence in astrophysics and cosmology …

David Wallace
Pittsburg University

Quantum gravity at low energies Read More »

Poster for Don Marolf's virtual seminar: Spacetime wormholes, superselection sectors, and ensembles in quantum gravity: An Overview

Don Marolf
University of California Santa Barbara

Spacetime wormholes, superselection sectors, and ensembles in quantum gravity: An Overview

Don Marolf will review and summarize recent developments regarding spacetime wormholes in the gravitational path integral and their implications for the existence of a certain notion of “superselection sectors” in quantum gravity.  The existence of such sectors implies that, in certain contexts, we can think of quantum gravity as describing a statistical ensemble of theories.  …

Don Marolf
University of California Santa Barbara

Spacetime wormholes, superselection sectors, and ensembles in quantum gravity: An Overview Read More »

Chris Smeenk Joins QISS. Expanded Visiting Philosophers Program.

We are happy to welcome Chris Smeenk to the consortium. Chris is the director of the Rotman Institute of Philosophy and professor of philosophy at Western University. In partnership with the Rotman Institute of Philosophy the current QISS visiting program aimed at philosophers will be significantly expanded, with the aim to train a new generation of philosophers of …

Chris Smeenk Joins QISS. Expanded Visiting Philosophers Program. Read More »

Richard Howl
Oxford University

Testing quantum gravity with non-Gaussianity and a Bose-Einstein condensate

Due to rapid progress in experimental quantum information science, a table-top test of quantum gravity may soon be possible. A promising possibility is to place two micro-solids in a spatial superposition and separable state. If, after a short time, entanglement between the micro-solids is observed then this could provide evidence of a quantum theory of gravity, assuming all other interactions can be neglected and that gravity provides a local interaction. These proposals have raised a number of questions, such as whether entanglement generation would really provide a test of quantum gravity and whether the experiments are feasible in the near term. Here, we consider whether an alternative signature of quantum gravity to entanglement could be used for a table-top test, and an alternative experimental setting. Specifically, we consider non-Gaussianity rather than entanglement and how this could be searched for in a Bose-Einstein condensate (BEC) to evidence quantum gravity. We discuss whether using non-Gaussianity and a BEC could provide any advantages to entanglement and micro-solids.