Quantum theory

We’re investigating novel forms of superfluidity created in ultracold atomic gases by undertaking the following research projects. 

Our research projects

Quantum entanglement and Bell non-locality in macroscopic systems 

This project explores two of the strangest non-classical features of quantum physics in the least expected situation of macroscopic systems. It is relevant to the foundations of quantum theory and to technological applications in cyber security.

Macroscopic Bell non-locality is being studied for double well BEC systems with two hyperfine components based on the Collins-Gisin-Linden-Massar-Popescu Bell inequalities.

Grassmann phase space theory for cold Fermi gases

This project applies phase space theory to cold Fermi gases using a non-standard version based on Grassmann phase space variables. The aim is to study phenomena such as the BEC/BCS crossover associated with Feshbach resonance, a project on which experiments are being carried out in the OSC. It is relevant to understanding the basic physics for such situations and to developing new methods for numerically treating fermion systems. 

Quantum correlation functions (QCF) describing the separation between fermions in a single Cooper pair and the correlation between the fermion positions in two Cooper pairs are being studied as a function of temperature for situations ranging from the BCS end of the crossover to the BEC end, with particular emphasis on the unitary regime where the fermion-fermion interactions become very strong. A theory of how to measure the QCF describing the positions in two Cooper pairs based on a four-mode version of Bragg spectroscopy is being developed.

Phase space theory for cold Bose gases

This project applies standard phase space theory to cold Bose gases. The aim is to study phenomena such as discrete Floquet time crystals in periodically driven cold Bose gases, a project on which an experiment is being carried out in the OSC. It is relevant to understanding the basic physics for such systems, including how time crystals can be created.

The onset of period-doubling and the breakdown of period T time symmetry for a BEC dropped onto a mirror oscillating with period T is being treated using the truncated Wigner approximation in phase space theory, with the aim of studying the effects of quantum fluctuations and the breakdown of mean field theory based on the Gross-Pitaevski equation. This research is in support of the experimental project led by Professor Hannaford.

Our team

• Professor Bryan Dalton (team leader)
• Mr Nader Kidwani (Project 2; PhD student)
• Professor Peter Hannaford (collaborator for project 2)
• Dr Jia Wang (collaborator for project 3)
• Professor Margaret Reid (collaborator for project 1)
• Professor Barry Garraway (University of Sussex, UK; collaborator for project 1)
• Professor Stephen Barnett (University of Glasgow, UK; collaborator for project 2)