non-equilibrium phases of matter and their applications to quantum information

Lead Research Organisation: University College London
Department Name: Physics and Astronomy

Abstract

"Broadly speaking, the goal of my PhD project is to investigate non-equilibrium phases of matter and their applications to quantum information. To provide some focus, we plan to partly concentrate our efforts on discrete time crystals (DTCs), a recently discovered non-equilibrium phase. DTCs are periodically-driven, or 'Floquet', systems, and as part of the PhD we hope
to develop some tools to study these systems. We are also currently collaborating with experimentalists on observations of DTCs, and we plan to continue this throughout the PhD."

Publications

10 25 50

Studentship Projects

Project Reference Relationship Related To Start End Student Name
EP/P510270/1 31/03/2016 30/08/2022
2075659 Studentship EP/P510270/1 24/09/2017 29/09/2021 Oliver Harry Lunt
 
Description Most of us learn in school about different "phases of matter". The main three you might have heard of are "solids", "liquids", and "gases". But it turns out that there are many more phases of matter, often with interesting properties which potentially could be useful for technological applications. For this reason, physicists have long been interested in discovering which phases of matter can exist, and what their distinguishing properties are. Mostly the focus has been on "equilibrium" phases of matter, where the fundamental properties of the phase do not change in time---if you put a lump of rock in a vacuum and left it for a million years, it will still look like a lump of rock when you come back. However, in recent years interest has developed in "non-equilibrium" phases of matter. These phases are in some ways much like conventional phases of matter, in that they are "emergent phenomena" arising from the interactions of many particles, and that they are stable against small changes to the underlying microscopic details. The main difference is that these "non-equilibrium" phases involve time in a fundamental way. If you leave some H20 molecules in close proximity to each other at room temperature, they will quickly form a liquid, namely water, and stay that way. On the other hand, these "non-equilibrium phases" require some external time-dependent input, such as a drive from a laser beam, upon which they start to display examples of this collective behaviour which characterizes phases of matter.

The interesting thing is that, by relaxing the requirement of equilibrium, we have opened up a whole new zoo of phases of matter, which fundamentally weren't possible in equilibrium. Probably the most famous example of a non-equilibrium phase is a "time crystal", proposed in 2012, and first probed in experiments in 2017. Technically, time crystals are defined as systems which "spontaneously break time-translation symmetry", in analogy to how conventional spatial crystals spontaneously break spatial-translation symmetry. Time crystals should be seen as the first stepping stone to exploring this new world of non-equilibrium phases of matter.

This award has funded some work which was done in collaboration with John Morton's experimental spin qubit group at UCL. In their lab they had observed signatures of what looked like time-crystalline behaviour, but in a system with quite different properties to previous experiments, namely one with strong dissipation. This suggested a novel mechanism for forming a time crystal. We worked with them to propose a theoretical model for their experiment.
Exploitation Route This work explores different mechanisms to produce novel phases of matter. However, given that the idea of a non-equilibrium phase of matter has only really existed since 2012, this field remains quite unexplored. Thus this work can be seen as a stepping stone to discovering new non-equilibrium phases of matter, some of which may have useful technological properties.
Sectors Aerospace, Defence and Marine,Chemicals,Digital/Communication/Information Technologies (including Software),Electronics,Energy,Manufacturing, including Industrial Biotechology

URL https://arxiv.org/abs/1807.09884