Virtual Seminars

Abhay Ashtekar
Pennsylvania State University

The many faces of photons

In the standard Fock representation, the 1-photon Hilbert space is spanned by positive frequency, source-free solutions of Maxwell’s equations. The quantum information they carry corresponds precisely to the two radiative modes of the Maxwell fields.  However, this Fock representation is inadequate in a number of physical situations involving sources, and one then has to use appropriate non-Fock representations. …

Abhay Ashtekar
Pennsylvania State University

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Wayne Myrvold
Western University

A Tale of Two Sciences, Both Called “Thermodynamics”

It has been occasionally remarked, but insufficiently appreciated, that there are two distinct sorts of endeavour that have gone by the name of “thermodynamics”. The first, which is in line with how the founders of the subject thought of it, is a theory about how agents with limited means of manipulation and limited access to …

Wayne Myrvold
Western University

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poster for Alexander Blum's virtual seminar, John Wheeler and Quantum Gravity, 7 december 2022, 4pm CET

Alexander Blum
  Max Planck Institute for the History of Science

John Wheeler and Quantum Gravity

John Wheeler was the inventor of quantum gravity – not as a formal program for uniting general relativity and quantum mechanics, but as the potential key to a theory of everything. In this talk, I will show how he first imbued quantum gravity with this new role in the 1950s and then how (and why) …

Alexander Blum
  Max Planck Institute for the History of Science

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Poster for Vlatko Vedral's QISS Virtual Seminar on 17 November at 4pm CET: Interference in QFT: detecting ghosts with phases

Vlatko Vedral
University of Oxford

Interference in quantum field theory: detecting ghosts with phases

I intend to discuss the implications of the principle of locality for interference in quantum field theory. As an example, I will consider the interaction of two charges via a mediating quantum field and the resulting interference pattern, in the Lorenz gauge. Using the Heisenberg picture, I will claim that detecting relative phases or entanglement between …

Vlatko Vedral
University of Oxford

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poster for the virtual seminar of Martin Plenio, 27 October at 5pm CEST testing quantum aspects of gravity at low energies

Martin Plenio
  Ulm University

Testing of Quantum Aspects of Gravity at Low Energies: Discussion of Experiment Aspects and Possible Loopholes

Testing the quantum character of weak forces such as gravity requires both exquisite experimental control of technology and careful design by theory of the experiment set-up. At the same time, the interpretation of experiments that probe the interface between quantum physics and gravity also mandates that we examine carefully all the assumptions, however innocuous, that …

Martin Plenio
  Ulm University

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Poster for Ivan Agullo's Virtual Seminar Talk title "Entanglement in Quantum Field Theory", 4pm CEST

Ivan Agullo
Louisiana State University

Entanglement in quantum field theory

It is well known that, even the simplest states within the simplest field theories, are highly entangled. The main support for this fact comes from calculations of entanglement entropy between a region of space and its complement. I find two uncomfortable facts in the calculation of such entropy: (i) The result is actually infinite, and …

Ivan Agullo
Louisiana State University

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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