The University of Southampton

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Date:
13th of October, 2022  @  13:00 - 14:00
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Date:
6th of October, 2022  @  13:00 - 14:00
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Date:
14th of October, 2022  @  13:00 - 14:15
Venue:
Microsoft Teams

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​Whether gravity is quantized remains an open question. To shed light on this problem, various Gedanken experiments have been proposed. One popular example is an interference experiment with a massive system that interacts gravitationally with another distant system, where an apparent paradox arises: even for spacelike separation the outcome of the interference experiment depends on actions on the distant system, leading to a violation of either complementarity or no-signaling. A recent resolution shows that the paradox is avoided when quantizing gravitational radiation and including quantum fluctuations of the gravitational field. Here I will show that the paradox in question can also be resolved without considering gravitational radiation, relying only on the Planck length as a limit on spatial resolution. Therefore, in contrast to conclusions previously drawn, we find that the necessity for a quantum field theory of gravity does not follow from so far considered Gedanken experiments of this type. In addition, I will present a setup where quantization is also not sufficient to resolve the paradox. This highlights that no Gedanken experiment to date compels a quantum field theory of gravity, in contrast to the electromagnetic case.

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- Event

Date:
9th of December, 2022  @  15:00 - 16:15
Venue:
Microsoft Teams

Event details

Lattice QCD is a powerful first-principles approach to QCD at low energies. Despite its success, lattice QCD calculations suffer from critical slowing down as the continuum limit is approached. Promising results suggest that machine-learned flow-based algorithms may instead provide efficient sampling of gauge field configurations in various lattice field theories. In this talk, I will review the recent progress applying these methods to lattice gauge theories.

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- Event

Date:
21st of October, 2022  @  13:00 - 14:15
Venue:
Teams

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​We introduce the importance of edge modes in the evaluation of entanglement entropy of subregions in U(1) gauge theory. We evaluate the contribution of these modes towards the universal logarithmic coefficient of entanglement across a spherical spatial region in U(1) gauge theory in even d dimensions. We show that this agrees with the logarithmic divergent part of the edge Harish-Chandra character of the theory on the d-sphere. We then consider the theory of linearized gravitons in 4 space-time dimensions. Quantizing the theory in tensor spherical harmonics we evaluate the contribution of the edge modes of the graviton towards the entanglement of a spatial region. We observe that this coefficient coincides with that extracted from the edge Harish-Chandra character of the massless spin-2 field on the S^4.

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- Event

Date:
7th of October, 2022  @  13:00 - 14:15
Venue:
46/5081 and on Teams

Event details

​Entanglement entropy of quantum fields is a topic of growing importance in several areas such as quantum gravity, condensed matter physics, and quantum information. In this talk I will review a formulation of entanglement entropy for Gaussian theories, in terms of the spacetime two-point correlation function. One of the attractive features of this formulation is that it makes it possible to use a UV cutoff that is spacetime in nature. I will discuss applications of this formulation in settings in both continuum spacetimes and discrete causal sets, as well as extensions to non-Gaussian and interacting theories.

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Published: 21 September 2022
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Dr. Bipasha Chakraborty

Atos and the Science and Technology Facilities Council (STFC) Hartree Centre have awarded the Joseph Fourier Prize, aimed at supporting innovative work in the field of quantum computing, to Doctor Bipasha Chakraborty, a lecturer in lattice QCD and a Leverhulme Trust Early Career Fellow who has recently joined the University of Southampton, for her research project ‘Quantum Computation of Quantum Field Theories’. The competition encourages academics and industrial scientists in quantum computing to submit their research proposals for a chance to win €10,000 to support their work. Each submission was carefully reviewed, and the winner selected by expert panelists from the Hartree Centre and Atos. The winning project aims to advance the application of Quantum Computation (QC) to solve complex equations in Quantum Field Theories (QFTs). These equations can be extremely difficult to tackle through classical computation, in part for giving rise to ‘sign problems’ – i.e., results yielding negative probabilities, which present no viable solutions. Professor Nicholas Evans, Head of Theory Group in Physics and Astronomy, commenting on Dr. Chakraborty's achievement said: " The Lattice QCD group in Southampton has for many years been an internationally leading centre for the study of the strong nuclear force using supercomputer simulations. Their work remains crucial for the search for new physics for example through recent measurements of the interactions between muons and magnetic fields and also decays of particles containing bottom quarks at the LHC. Dr. Bipasha Chakraborty who has recently joined the group brings new expertise to this core programme. In addition, she is amongst the first in the world to explore quantum simulations of complicated quantum systems which should in the future provide faster and more accurate results." Dr. Chakraborty’s research has already produced some of the first digital QC algorithms to solve complex QFTs with sign problems, and the Joseph Fourier Prize will support her work in creating pathways for digital QCs of even more complex QFTs, such as in Quantum Chromodynamics. Ultimately, approaching the sign problem through Quantum Computation can help address a diverse range of real-life problems – for example, in understanding aspects of quantum chemistry and the unique properties of graphene, calculating electron distribution in complex biomolecules, and many other transformative industry test cases. At a theoretical level, this line of research can contribute towards a paradigm shift in our current understanding of the Standard Model of Particle Physics. Philipp Strasmann – Head of Big Data & Security Northern Europe, Atos said: “As the first such competition in the UK to support and celebrate researchers’ own work, we hope this prize will encourage further vital quantum research, driving awareness and stimulating local interest and talent for this vitally important subject area.” Michael Gleaves, Hartree Centre Deputy Director, said: “We are on the cusp of a quantum revolution, and at this crucial stage we must encourage and promote independent research that helps apply theory to practical quantum computing use. We are pleased to have identified a winner of the inaugural prize and to have partnered to deliver it.” Atos Quantum Program aims to develop a comprehensive, enterprise-grade quantum computing environment for the future. It features, among other tools, the Quantum Learning Machine – the most powerful quantum emulator platform on the market. Atos takes a leadership role within the High-Performance Computing industry through initiatives such as the Joseph Fourier Prize, and is a strategic partner to the Hartree Centre – which works with industry and the research community to address real-life challenges and accelerate the adoption of digital technologies. Dr. Bipasha Chakraborty said: "This is a very welcome acknowledgement of my innovative research proposal in Quantum Computation of Quantum Field Theories and provides welcome support to push it forward. The prize also offers a platform to initiate collaboration with industries, which is critical to the success of this interdisciplinary research.” Dr Bipasha Chakraborty is joining the group bringing new expertise to this core programme. In addition, she is amongst the first in the world exploring quantum simulations of complicated quantum systems which should in the future provide faster and more accurate results. A long standing problem in the field has been how to study quarks at high density (such as in neutron stars or in heavy ion collisions) and Bipasha has shown how quantum simulation could overcome these problems. The award of the Joseph Fourier Prize rewards this work and hints to the exciting potential for the future. The P&A theory group in Southampton looks forward to being at the forefront of the quantum computing revolution. Professor Nicholas Evans, Physics and Astronomy, FEPS "A long-standing problem in the field has been how to study quarks at high density (such as in neutron stars or in heavy ion collisions) and Bipasha has shown how quantum simulation could overcome these problems. The award of Joseph Fourier Prize rewards this work and hints at the exciting potential for the future. The P&A theory group in Southampton looks forward to being at the forefront of the quantum computing revolution", concludes Prof. Evans.

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