Ultracold Gases far from Equilibrium: Fluctuations in time-dependent Geometries

Lead Research Organisation: Newcastle University
Department Name: Mathematics and Statistics

Abstract

Intensive research over the last 15 years has shown that one can cool atoms in a gas by suitable use of magnets and light to a tiny fraction above absolute zero, the temperature at which all motion freezes. At such a low temperature, atoms suddenly experience an 'identity crisis', and are coerced into behaving identically - what is scientifically termed 'coherently'. Because these 'ultracold' atoms are almost stationary, they can actually become sensitive 'measuring devices' of effects they would otherwise essentially not feel, such as gravity, or magnetic fields. Suitable devices have been constructed to take advantage of this, and are known as 'atom interferometers'. In such devices, a group of trapped, very cold atoms is split into two smaller groups of approximately equal size in physically-separated locations, and then subsequently joined together again. A study of the properties of the atoms after they are joined reveals important information about changes in phenomena taking place when they were separated (e.g. changes in the strength of gravity between the two separated locations). Such a 'measuring device' has essentially two variants, depending on whether the atoms were originally stationary or moving, with each scheme having its own benefits and shortcomings. In order to take full advantage of such devices, one should develop a detailed understanding of the physical processes that take place in such systems, and this project intends to make significant advances in this area.A detailed description of such systems is complicated by the fact that at the typical temperatures where most current experiments take place, only some of the atoms behave 'coherently', with the rest of the atoms behaving in a random fashion, just like atoms in the air around us. Moreover, our ability to control the motion of atoms appears to be enhanced in thin long geometries, but this significant benefit is partly counterbalanced by the tendency of such geometries to destroy the 'coherent' nature of the system; the latter is due to fluctuations (in the phase of the system) which arise as a fundamental consequence of quantum mechanics, the theory which describes the microscopic world. Any theoretical model attempting to describe such experiments accurately should take account of these issues.The main aims of this project are two-fold: (i) firstly, to perform an in-depth study of fundamental physical mechanisms which may restrict the accuracy of such devices. (ii) Secondly, this project addresses the crucial question of how feasible it is to produce in a controlled manner a beam of atoms which maintain their coherence, even though they are actually moving, a topic of great current interest. Although there are numerous related theoretical studies in the literature, this work is unique in that it combines essential features that have to date only been implemented in independent studies: (i) firstly, this study is performed under realistic conditions, in which only some of the atoms behave coherently, and includes the full dynamics of both 'coherent' and 'random' atoms and their interactions. (ii) Moreover, additional complications (phase fluctuations) arising from the fact that these systems are very thin and long are also treated by advanced (stochastic) techniques, which are naturally 'built into' the approach mentioned above, with such a generalised theory solved numerically for the first time in the present work.Motivated by recent pioneering experiments which remain only partly understood, we use computers to study how the properties of the atoms are affected upon changing various parameters of the system, such as geometry, size and temperature, and we further investigate related issues in moving atoms.
 
Description This project was aimed at obtaining an improved, more detailed, understanding of the behaviour of ultracold gases - a system of interest to both experimentalists and theorists - as it enables the pure study of quantum effects in a relatively large system, in which cold atoms behave 'in unison', exhibiting interesting phenomena below a certain characteristic temperature; this is particularly true in experiments in which the dominant processes occur in only one or two dimensions, which enhances the role of fluctuations. Understanding, and harnessing, such non-equilibrium processes in the presence fluctuations is of significant importance in potential devices based on such systems. This work provided a detailed framework for understanding such systems, and was tested against experiments from the key international groups, generating specific scientific outcomes.
Exploitation Route If the applications mentioned above (atom chips, atom lasers, atom interferometers) were to become more broadly accessible outside academia in the future (e.g. to industrial sector related to quantum technologies), then this work could be seen as having an indirect contribution to such devices. The outcomes of this research are relevant to both experimentalists and theorists dealing with ultracold atoms and their dynamics, and indirectly might help optimize future devices.
Sectors Education,Other

URL http://www.jqc.org.uk/people/nick-proukakis/29/
 
Description Other research groups have benefited from the outcomes of this grant, implementing, or building upon our techniques. It has also led to discussions with experimentalists, who are themselves engaged in discussions with industry about the possibility of forming new, or enhancing existing quantum technologies. The research led to the compilation of a computing manual for future researchers.
First Year Of Impact 2013
Sector Education,Other
 
Description IoP Student Fund
Amount £250 (GBP)
Organisation Institute of Physics (IOP) 
Sector Learned Society
Country United Kingdom of Great Britain & Northern Ireland (UK)
Start 06/2011 
End 06/2011
 
Description Royal Society Travel Award
Amount £1,100 (GBP)
Organisation The Royal Society 
Sector Academic/University
Country United Kingdom of Great Britain & Northern Ireland (UK)
Start 06/2010 
End 06/2010
 
Description Comparison of stochastic techniques for finite temperature Bose gases 
Organisation University of Ulm
Country Germany, Federal Republic of 
Sector Academic/University 
PI Contribution Presentation of joint collaborative work at German Physical Society meeting DPG Tagung 14 March 2011, Dresden
Start Year 2009
 
Description Visiting Academic 
Organisation University of Queensland
Country Australia, Commonwealth of 
Sector Academic/University 
PI Contribution Invited to visit the University of Queensland to discuss joint research interests. This resulted in one joint publication to date, and an additional book chapter in preparation. Moreover, 3 members of that group have since visited Newcastle University for periods of 1-12 weeks for related discussions,
Start Year 2010
 
Description Visiting Professorhsip 
Organisation Eberhard Karls University of Tubingen
Country Germany, Federal Republic of 
Sector Academic/University 
PI Contribution Invited visit to discuss possible theoretical-experimental joint research opportunities
Start Year 2011
 
Description Visiting Professorhsip 
Organisation Queen's University
Country Canada 
Sector Academic/University 
PI Contribution Inivited to visit Queen's University, Kingston, Canada to discuss related research issues.
Start Year 2010
 
Description Visiting Professorhsip 
Organisation University of Toronto
Country Canada 
Sector Academic/University 
PI Contribution Invited to visit Toronto University to discuss related research issues
Start Year 2010
 
Description 'Modelling Quasi-condensate atom chip experiments' and 'Decay of macroscopic excitations in atomic condensates' 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Participants in your research and patient groups
Results and Impact Two research talks given in consecutive weeks at the University of Tubingen, Germany.

Very strong interfacing with key international research group; led to subsequent research publication.
Year(s) Of Engagement Activity 2011
 
Description Dark soliton dynamics in atomic Bose condensates 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Participants in your research and patient groups
Results and Impact Invited talk during my visiting professorship at Toronto:

2010 May 11 Canada Department of Physics, University of Toronto.

Prmotion of my research to a borad community
Year(s) Of Engagement Activity 2010
 
Description Dark soliton dynamics in atomic condensates 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Participants in your research and patient groups
Results and Impact Invited seminar during my academic visit there

2010 Jul 6 Australia School of Mathematics and Physics, The University of Queensland, Brisbane.

Borad disemmination of research findings
Year(s) Of Engagement Activity 2010
 
Description Finite temperature properties of fluctuating trapped atomic quasi-condensates 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Participants in your research and patient groups
Results and Impact Invited seminar

Nov 18 U.K. School of Physics and Astronomy, University of Birmingham.

Making research connections within the UK
Year(s) Of Engagement Activity 2011
 
Description How to model ultracold Bose gases at nonzero temperatures 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Participants in your research and patient groups
Results and Impact 3-hour graduate teaching/research seminar

2011 Mar Austria Atominstitut, Vienna University of Technology.

Education of pre-PhD students at an international institute
Year(s) Of Engagement Activity 2011
 
Description Modelling Finite Temperature Bose Gases 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Participants in your research and patient groups
Results and Impact 2009 Dec Germany Joint Atomic & Condensed Matter Physics Seminar Series

Universities of Stuttgart, Tuebingen and Ulm (Tuebingen)
.

INternational profile raising
Year(s) Of Engagement Activity 2009
 
Description Modelling quasi-1D Bose gases via the Stochastic Gross-Pitaevskii equation 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Participants in your research and patient groups
Results and Impact Invited research seminar

2011 Mar 2 U.K. School of Physics and Astronomy, University of Leeds.

Interfacing with colleagues from broader research interests.
Year(s) Of Engagement Activity 2011
 
Description Modelling quasi-1D Bose gases with the stochastic Gross-Pitaevskii equation 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach Regional
Primary Audience Participants in your research and patient groups
Results and Impact Invited Departmental Seminar:

Durham Atomic and Molecular Physics ( ATMOL) Group seminar, UK

(16th March 2011 ).

Disemmination of novel research results
Year(s) Of Engagement Activity 2011
 
Description Non-Equilibrium Ultracold Bose Gases 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Participants in your research and patient groups
Results and Impact Invited departmental seminar

2010 Feb 18 U.K. Department of Physics, University of Southampton.

Discussions with colleagues
Year(s) Of Engagement Activity 2010
 
Description Soliton propagation in trapped quantum gases 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Participants in your research and patient groups
Results and Impact INvited seminar during my visiting professorship

2010 23 Apr Canada Department of Physics, Engineering Physics and Astronomy, Queen's University, Kingston.

International research networking
Year(s) Of Engagement Activity 2010
 
Description Stochastic Modelling of Quasi-condensates 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Participants in your research and patient groups
Results and Impact Invited Seminar at:

2011 18 July Germany Department of Physics, University of Freiburg.

Research links with key german UNiversity; led to research visit to the UK
Year(s) Of Engagement Activity 2011
 
Description Ultracold Trapped Atoms: A fully controllable condensed matter system 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Participants in your research and patient groups
Results and Impact Invited departmental colloquim

2010 Mar 25 Greece

Dept. of Applied Mathematics and Theoretical Physics, National Technical University of Athens.

Interfacing with international colleagues of different specialisations.
Year(s) Of Engagement Activity 2010
 
Description Ultracold Trapped Atoms: A fully controllable macroscopic quantum system 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Participants in your research and patient groups
Results and Impact Invited departmental seminar

2010 Mar 18 Greece Department of Physics, University of Athens.

interfacting with non-experts in my field
Year(s) Of Engagement Activity 2010