*Scroll down this page for upcoming seminar poster, program and past seminar archive.***Join**QISS Virtual Seminar by following the link hku.zoom.us/j/728065144 or using the Zoom Meeting ID 728 065 144. Alternatively, watch the seminar

**live**on the QISS youtube channel. All seminars are archived and available to watch at a later time on our youtube channel.

(The `Zoom client for meetings' can be downloaded here: zoom.us/download)

Seminars are

**open**to participation.

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**The idea**

Seminar topics range from fundamental theory to experiments and the philosophy of science, in particular on questions at the intersection of Quantum Gravity, Quantum Information and Quantum Foundations. The

**goal is to stimulate discussion**across disciplines, rather than presenting incremental technical results pertinent only for specialists in a sub-field.

For this reason, the talk duration is relatively short (<30 mins) and speakers are encouraged to make it pedagogical. One or two commentators will first engage the speaker(s) for ~10mins to get the discussion going. After this stage, questions and comments are open to all participants for one hour.

*QISS Virtual Seminar organising committee: Pierre Martin-Dussaud, Lucas Hackl, Marios Christodoulou.*

The zoom meeting is hosted at The University of Hong Kong through its Quantum Information and Computation Initiative (QICi).

The zoom meeting is hosted at The University of Hong Kong through its Quantum Information and Computation Initiative (QICi).

## Upcoming QISS Virtual Seminar

Robert Oeckl July 16 by QISS Initiative

**The invention of quantum theory in the 1920s represented a paradigm shift in our approach to describing the natural world. The focus on the object as a primitive shifted to the observation as a primitive. At the time, the first applications of interest came with a classical description in the language of Hamiltonian evolution, canonical variables and states. Staying close to this particular language lead to the development of the quantum formalism of Hilbert spaces, operators, Schrödinger equation and Born rule. Somewhat unfortunately, this standard formulation has come to dominate our understanding of what quantum theory is. While it was successfully employed in describing the micro-structure of matter and its relevant interactions, describing the dynamics of spacetime itself is outside of its scope. With the present talk I want to promote the idea that quantum theory is much more general than this standard formulation. I aim to clarify the essence of the paradigm shift that lies at the heart of the transition from classical to quantum theory. On this basis I then review the derivation from first principles of a more fundamental formulation of quantum theory, the positive formalism, and the recovery of the standard formulation as a special case.**

Talk abstract:

Talk abstract:

**Autumn 2020 Series**

(check at a later point for updates)

(check at a later point for updates)

1st of September: TBA

22nd of September: Alejandro Perez

8th of October: Nick Huggett

29th of October: TBA

19th of November: TBA

2nd of December: Jennan Ismael

## Past/Archived Seminars

**Speaker**

Chiara Marletto

University of Oxford

**Date and Time:**

**July 2, 2020**

Watch archived seminar on youtube

Watch archived seminar on youtube

**Title**

Witnessing non-classicality beyond quantum theory

**Abstract**

After briefly discussing constructor theory (a recently proposed generalisation of the quantum theory of computation), I will present the general argument that provides a robust theoretical underpinning for the recently proposed experiments to witness quantum effects in gravity.

**Speaker**

Sougato Bose, University College London

**Date:**

**May 14, 2020**

**Watch archived seminar on youtube**

**Title**

Table-top Testing of the Quantum Nature of Gravity: Assumptions, Implications and Practicalities of a Proposal

**Abstract**

A lack of empirical evidence has lead to a debate on whether gravity is a quantum entity. Motivated by this, I will present a feasible idea for such a test based on the principle that two objects cannot be entangled without a quantum mediator. I will show that despite the weakness of gravity, the phase evolution induced by the gravitational interaction of two micron size test masses in adjacent matter-wave interferometers can detectably entangle them even when they are placed far apart enough to keep Casimir-Polder forces at bay. A prescription for witnessing this entanglement, which certifies gravity as a quantum coherent mediator, is also provided and can be measured through simple spin correlations. Further, I clarify the assumptions underpinning the above proposal such as our reasonable definition of "classicality", as well as the crucial aspect of the locality of physical interactions. The role of off-shell processes is also highlighted to clarify what the mediators actually are according to the standard theory of quantum gravity. How the experiment sits within relativistic quantum field theory is clarified. Lastly, a list of practical challenges are noted.

**Speaker**

Eugenio Bianchi, Penn State University

**Date and Time:**

**Watch archived seminar on youtube**

**April 23, 2020, 3PM GMT**

**Title**

Entanglement and the Architecture of Spacetime

**Abstract**

The quantum field vacuum is highly entangled, even in causally disconnected regions. In contrast, the state of a quantum geometry of space can be unentangled, resulting in an uncorrelated network of elementary quanta of space. In this talk I discuss how the architecture of spacetime emerges from entanglement between these elementary quanta. I will focus on loop quantum gravity, causal structures and the primordial universe.

**Speakers**

Jeremy Butterfield and Henrique Gomes, University of Cambridge

**Date and Time:**

**Watch archived seminar on youtube**

**April 2, 2020, 3PM GMT**

**Title**

On Reduction and Functionalism about Space and Time.

**Abstract**

Various programmes and results in the philosophy/foundations of spacetime theories illustrate points about reduction and functionalism in general philosophy of science. I will focus on some programmes and results about how the physics of matter contributes to determining, or even determines, or even explains, chrono-geometry. I will say something about most of the following examples: the Helmholtz-Lie theorem on free mobility implying constant curvature; and in the philosophical literature, Robb (1914), and Mundy (1983). I also hope to mention from the physics literature: Barbour and Bertotti (1982), Hojman, Kuchar and Teitelboim (1976); Dull, Schuller et al. (2012, 2018); and Gomes & Shyam (2016: 1608.08236 = J. Math. Phys. 57, 112503).