Superfluid helium is a quantum liquid that exhibits a range of counter-intuitive phenomena such as frictionless flow. Quantized vortices are a particularly important feature of superfluid helium, and all superfluids, characterized by a circulation that can only take prescribed integer values. However, the strong interactions between atoms in superfluid helium prohibit quantitative theory of vortex behaviour. Experiments have similarly not been able to observe coherent vortex dynamics. This thesis resolves this challenge, bringing microphotonic techniques to bear on two-dimensional superfluid helium, observing coherent vortex dynamics for the first time, and achieving this on a silicon chip. This represents a major scientific contribution, as it opens the door not only to providing a better understanding of this esoteric quantum state of matter, but also to building new quantum technologies based upon it, and to understanding the dynamics of astrophysical superfluids such as those thought to exist in the core of neutron stars.

Auteur
Dr Sachkou completed his undergraduate degree in physics with a specialisation in laser systems at the Belarusian State University in Minsk, Belarus. He then obtained Master of Science in Photonics degree jointly from Ghent University, Vrije Universiteit Brussel (both Belgium), and University of St Andrews (Scotland). Yauhen received a PhD in physics from the University of Queensland, Australia in 2019.
Dr Sachkou's expertise covers a range of concepts of modern physics from superconducting circuits to quantum fluids and optomechanics, with the particular focus on quantum technologies. Apart from academic research, Yauhen enjoys engaging in various science communication and outreach activities.

Contenu
Introduction and Overview.- Optomechanical Platform for Probing Two-Dimensional Quantum Fluids.- Light-Mediated Control Of Superfluid Flow.- Theoretical Investigation of Vortex-Sound Interactions In Two-Dimensional Superfluids.- Observation of Coherent Vortex Dynamics in Two-Dimensional Superfluid Helium.- Summary.- Appendices.