17 November 2021
Iacopo Carusotto (Universitá di Trento)
Quantum Fluids of Light
In this colloquium, we will give an overview of the emerging field of quantum fluids of light: in the presence of a finite effective mass due to light confinement and binary interactions mediated by the optical nonlinearity of the material medium, an assembly of photons behaves as a fluid of particles and displays intriguing hydrodynamic phenomena.
After reviewing early work on Bose-Einstein condensation and superfluidity in such systems, I will sketch some among the most exciting recent developments at the crossroad of many-body physics, non-equilibrium statistical mechanics, and quantum optics.
The new features of topological lasing, aka non-equilibrium condensation into a topological edge mode, are capturing the interest of a wide community spanning across fundamental and applied research, from a remarkable topological protection of long-distance phase-locking to fabrication disorder to Kardar-Parisi-Zhang features in the emission coherence.
Strong efforts are presently devoted to the realization of strongly quantum correlated phases of photonic matter in a novel non-equilibrium context. After presenting recent realizations of Mott insulator and baby fractional quantum Hall fluids, I will sketch the new perspectives that these advances are opening for many-body physics and quantum technologies in general.
1 December 2021
Christopher Monahan (William & Mary)
Peering inside the proton
Calculating the internal three-dimensional structure of protons and neutrons has been a long-standing goal for nuclear physics. The strong nuclear force binds together quarks and gluons into protons, neutrons and other hadrons, but the strongly coupled nature of the strong force ensures that calculations of hadron structure are very challenging. Recent theoretical developments mean these calculations, using lattice quantum chromodynamics (QCD), have now become possible. Last year, the first proof-of-principle calculations of generalised parton distributions, which capture the correlations between the longitudinal momentum structure of nucleons and their transverse structure, marked the advent of a new era in lattice QCD calculations of hadron structure. I introduce the ideas that underpin these developments, and summarise some of the most exciting recent results.
15 December 2021
Janet Anders (Exeter)
Quantum Brownian Motion for Magnets
 Quantum-classical transition of steady states and mean force Gibbs states in the spin boson model,
26 January 2022
Hannah Price (Birmingham)
Quantum Simulation with Synthetic Dimensions
9 February 2022
Tom Hayward (Sheffield)
From Stochasticity to Functionality: Harnessing Magnetic Domain Walls for Probabilistic and Neuromorphic Computing
Domain walls (DWs) in soft, ferromagnetic nanowires have been a topic of intense research interest due to proposals to use them as data carriers in energy efficient, non-volatile logic and memory devices. However, despite their apparent technological potential, these devices have been challenging to realise, because DWs pinning and propagation is highly stochastic, making digital devices unreliable . While materials engineering approaches can be used to supress stochasticity , it is also interesting to consider whether alternative computer paradigms could prove more resistant to, or even benefit from, the DWs’ stochastic behaviours, thus converting it from a technologically inhibitive phenomenon into a functional property.
In this talk I will introduce the basic physical behaviours of domain walls in magnetic nanowires and show how these lead to complex and stochastic interactions between DWs and defect sites. I will then present a combination of experimental measurements and simulations that illustrate how these behaviours can be used to realise two different neuromorphic (brain-like) computing paradigms in hardware: feed-forward neural networks and reservoir computing . The work presented will include experimental demonstrations of how these devices can be used to performed benchmark machine learning tasks such as spoken/written digit recognition.
 T.J. Hayward and K.A. Omari, Beyond the quasi-particle: stochastic domain wall dynamics in soft ferromagnetic nanowires, Journal of Physics D: Applied Physics 50, 8, 084006 (2017).
 T.J. Broomhall, A.W. Rushforth, M.C. Rosamond, E.H. Linfield, and T.J. Hayward, Physical Review Applied 13, 024039 (2020).
 R. W. Dawidek, T. J. Hayward, I. T. Vidamour, T. J. Broomhall, M. Al Mamoori, A. Mullen, S. J. Kyle, P. W. Fry, N. J. Steinke, J. F. K. Cooper, F. Maccherozzi, S. S.Dhesi, L. Aballe, M. Foerster, J. Prat, E. Vasilaki, M. O. A. Ellis, D. A. Allwood, submitted to Advanced Functional Materials (2020).