Testing for Quantum Gravity with Bose-Einstein Condensates

The multimode collaborative work `Non-gaussianity as a Signature of a Quantum Theory of Gravity’ between Hong Kong, Aix-Marseille and Oxford you, lead by Richard Howl and with the participation of Marios Christodoulou, Carlo Rovelli and Vlatko Vedral, has been published in PRX Quantum. Below is an accessible to the non-specialist summary. For over a hundred years, physicists …

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Chiara Marletto featured at The Guardian

Chiara Marletto has been featured in the guardian,Chiara Marletto is a research fellow at Wolfson College, University of Oxford. Her research is in theoretical physics – especially quantum computation, thermodynamics and information theory. Her broader interests include theoretical biology, epistemology and Italian literature. The Science of Can and Can’t: A Physicist’s Journey Through the Land …

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Bob Wald
University of Chicago

Quantum Superposition of Massive Bodies

We analyse a gedankenexperiment previously considered by Mari et al. that involves quantum superpositions of charged and/or massive bodies (“particles”) under the control of the observers, Alice and Bob. In the electromagnetic case, we show that the quantization of electromagnetic radiation (which causes decoherence of Alice’s particle) and vacuum fluctuations of the electromagnetic field (which limits Bob’s ability to localize his particle to better than a charge-radius) both are essential for avoiding apparent paradoxes with causality and complementarity. We then analyze the gravitational version of this gedankenexperiment. We show that the analysis of the gravitational case is in complete parallel with the electromagnetic case provided that gravitational radiation is quantized and that vacuum fluctuations limit the localization of a particle to no better than a Planck length. This provides support for the view that (linearized) gravity should have a quantum field description.

Marcus Aspelmeyer
University of Vienna

On the role of gravity in table-top quantum experiments

I will discuss the challenges and prospects for isolating and exploring gravity as a relevant coupling mechanism in table-top quantum experiments. This includes quantum states of the metric generated by a quantum source mass and possible schemes to measure it. Experimentally, a central role is played by the possibility to achieve quantum control over motional states of levitated solid-state particles.

Aleks Kissinger
University of Oxford

Extending the logic of influence and causation

Abstract: I will talk about some recent developments in the framework of “black box causal reasoning”. In this minimal setting, we assume access to some abstract process and attempt to describe, quantify, or prove properties about the causal relationships between its inputs and outputs. This works both for first-order processes, which can capture e.g. a device shared by multiple agents, or higher-order processes, which captures the universe in which those agents live. This higher-order picture leads naturally to a particular categorical structure that has long been studied in theoretical computer science called a *-autonomous category. Whereas first order processes (e.g. quantum gates) only have two natural notions of composition (in series and in parallel), higher-order processes have an extremely rich and multi-faceted notion of composition guided by the “internal logic” of a *-autonomous category. In this talk, I will highlight some aspects of this logic, show how they can be used for causal reasoning, and discuss some recent extensions and open problems.