New Physics at the Interface Between the Classical and Quantum Worlds

Lead Research Organisation: University College London
Department Name: London Centre for Nanotechnology

Abstract

Condensed matter physics is an area of both technological and fundamental scientific importance. Modern technology isincreasingly dependent upon the quantum behaviour of matter on the smallest scale. The race to make a quantumcomputer seeks to use this behaviour very directly, but quantum mechanics is important in more familiar technology:transistors, superconductors and the read heads in hard drives all depend crucially upon the quantum mechanics ofelectrons in solids.Understanding the collective quantum behaviour of electrons in solids is not only an important driver of technology, but italso raises fundamental issues with impact in other areas of science. To take a topical example, the explanation of whysuperconductors hover in magnetic fields (the Meissner effect) was provided by the Anderson-Higgs mechanism --- thevery same mechanism that is now thought to provide the origin of mass itself and which is currently being investigated atFERMILAB the LHC in CERN.There is a tremendous symbiosis between theory and experiment in condensed matter physics. New theoretical ideas arecrucial in guiding experiment in fruitful directions and puzzling results from experiment are essential in aiding thedevelopment of theory --- unraveling these puzzles can lead to fundamental principles that have an impact much furtherafield.I study the theory of the collective quantum behaviour of electrons. I develop mathematical theories predicting neweffects not yet seen in experiment and work with experimentalists to understand how these new effects can be observed.Together, we determine which experimental anomalies might be understood within current theories. Those that cannotprovide important guidance and new directions for theoretical investigation.Much of my time is spent studying quantum critical systems. These systems are balanced between the quantum andclassical worlds --- they obey rules that are partly like the classical rules of everyday experience and partly the strangequantum rules of the very smallest scale. A large variety of materials have electronic behaviour that is quantum critical.They have a property that physicists call universality: their behaviour at low energy and long distances is largelyindependent of the high energy and short distance behaviour. Because of this, they provide a forum in which we canunderstand general features of how classical world emerges from the quantum behaviour on the microscopic scalewithout being distracted by details such as differences between materials.

Planned Impact

Profile: This proposal has the potential to generate fundamental advances that will inevitably enhance the profile of UK science. The UK has a world-leading effort in experiments on quantum critical systems, coordinated through programmes such as the EPSRC Portfolio Partnership Novel Quantum Order in Interacting Electron Metals . My programme aims to bring a similar visibility to UK theoretical efforts. The use of recently installed grid infrastructure promises to be a cost-effective new way of coordinating research across the UK. The enhanced interactions between theory and experiment that result will give tremendous leverage to research and will provide training for graduate students and post-doctoral researchers that is of greater relevance to industry. The scientific results of this research will advertise the breadth and quality of the UK skills base. Skills Base: a) Post-doctoral Fellows (PDRAs): The immediate training benefit would be felt by the PDRAs. My programme will afford them the opportunity to develop both cutting edge theoretical skills and the practical ability to apply them to experiments. St Andrews presents an excellent opportunity for these interactions due to its world-leading experimentalists and the established collaboration that I have with them. The PDRAs will engage with both the local group and with my international collaborative network. They will learn to manage these interactions towards our scientific goals and important mentoring skills through their work with graduate students. My broader network of collaborations will provide good opportunities for progression of PDRAs. I am well-placed to guide them towards contacts in the financial and technology sectors should they ultimately choose to pursue careers beyond academia. b) PhD Students: The University of St Andrews is one of the host institutions for the Scottish Doctoral Training Centre (DTC) in Condensed Matter Physics. It is essential for the success of the DTC that it is embedded within world-class research groups. My team will form an important part of this environment and will help enhance the theoretical training of graduate students. Conversely, my research team will benefit from the elite graduate students that the DTC attracts and from its programme of international visitors. Materials and Technology: Although focused upon fundamental physics, the work proposed here is likely to have longer term, technological impact. Strongly correlated electron materials will play a key role in future technologies. The timing and extent of this impact is impossible to judge in advance of discovery, but it is essential for future industry. I have engaged with industry in a variety of contexts including GEC Marconi Research, Lucent Technologies Bell Labs (now Alcatel) and start up companies such as Cambridge Magnetic Refrigeration. I am well placed to seek appropriate channels of exploitation should occasion arise. Public Outreach: I am committed to public outreach. I have given presentations in Schools and Colleges, at the Royal Institution and various Cafes Scientifique, and run a Cafe Scientifique in St Andrews. These provide many opportunities to bring the results of my research to a broader public. This work plays an important role in inspiring young students into possible careers in science. They will mesh well with the outreach program of the DTC, which will be run by the PhD students, and the Gateway to Physics programme organised jointly between St Andrew and Heriot Watt. The latter aims to encourage students from less advantaged backgrounds into physics and engineering. Public outreach also fulfils an important cultural role. These are exciting times in theoretical physics with new links being forged between apparently disparate areas. I aim to share this with the public. I will encourage my PDRAs to become involved in outreach and have requested funds for them to attend media training courses.

Publications

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Related Projects

Project Reference Relationship Related To Start End Award Value
EP/I004831/1 01/10/2010 01/11/2011 £1,315,346
EP/I004831/2 Transfer EP/I004831/1 01/11/2011 31/03/2016 £1,066,100
 
Description The collective properties of collections of many identical quantum particles pose some of the most challenging problems of modern physics. At the same time developing new analytical tools to address these is revealing commonality with challenges in disparate areas - connections between the sting theory of black holes and the field theory of certain electronic systems, and tensor network methods used to describe quantum systems and deep learning networks to give two pertinent cases.

This research funding has underpinned all of the major research directions of my group. There have been several key advances i. a new way to understand how fluctuations induce the formation of new quantum phases - this is useful in understanding novel material properties ii. A connection between fluctuation effects in certain metals and the Hawking radiation from black holes, as well as iii a connection between quantum field theory and tensor network descriptions of quantum systems.

Out of these, I have developed a number of research directions - in quantum materials with a grant combining theoretical analysis and experimental investigation, a programme to harness tensor network ideas and early stage quantum computers for quantum simulation and machine learning (in partnership with Bristol, Google and GTN), and a fundamental programme of research into out-of-equilibrium quantum dynamics .
Exploitation Route The results of this work are proving directly useful to the understanding of quantum systems and provide a useful way for experimentalists to understand novel strongly correlated phases. Other theoretical developments provide the underpinning to new understanding of quantum systems and ways to harness them to practical purposes.
Sectors Digital/Communication/Information Technologies (including Software),Education,Electronics

 
Description The development of the quantum order by disorder approach to understanding fluctuation induced quantum phases is continuing. One aspect of this is the potential to include these effects into ab initio codes. These codes are widely used in industry and success in this translation will propagate the impact quite far. The effort to make this inclusion in ab initio codes is well-underway with my graduate student Adam Walker. The study of adiabatic quantum computation has provided a seed for a useful alternative way to study the constraints of adiabatic computation. The work is beginning to have some traction and has been useful in our interactions on this subject with Lockheed Martin and Dwave computing. More recently these ideas have influenced my groups attempts to understand how to harness NISQ computers for quantum simulation.
Sector Digital/Communication/Information Technologies (including Software),Education
Impact Types Societal

 
Description EPSRC Responsive Mode
Amount £1,574,583 (GBP)
Funding ID EP/P013449/1 
Organisation Engineering and Physical Sciences Research Council (EPSRC) 
Sector Public
Country United Kingdom
Start 04/2017 
End 03/2021
 
Description Q trajectory ensembles 
Organisation City University of New York (CUNY)
Country United States 
Sector Academic/University 
PI Contribution My graduate student Philip Crowley and I are collaborating with Vadim Oganesyan on a trajectory ensemble approach to understanding the effects of coupling to the environment on quantum dynamics. We have committed ideas and time to the project. This has continued with my PhD student Fergus Barratt who is part of the CANES DTC at KCL. We have drafted a paper showing how the failure of adiabatic computation due to dephasing noise can be understood as a dynamical phase transition. This will be submitted imminently.
Collaborator Contribution Prof Vadim Oganesyan has similarly committed time and ideas to this project.
Impact None so far: see above. A paper is expected in weeks.
Start Year 2015
 
Description Q trajectory ensembles 
Organisation King's College London
Country United Kingdom 
Sector Academic/University 
PI Contribution My graduate student Philip Crowley and I are collaborating with Vadim Oganesyan on a trajectory ensemble approach to understanding the effects of coupling to the environment on quantum dynamics. We have committed ideas and time to the project. This has continued with my PhD student Fergus Barratt who is part of the CANES DTC at KCL. We have drafted a paper showing how the failure of adiabatic computation due to dephasing noise can be understood as a dynamical phase transition. This will be submitted imminently.
Collaborator Contribution Prof Vadim Oganesyan has similarly committed time and ideas to this project.
Impact None so far: see above. A paper is expected in weeks.
Start Year 2015
 
Description cMPS and CFT 
Organisation Brookhaven National Laboratory
Department Condensed Matter Physics & Materials Science Department
Country United States 
Sector Public 
PI Contribution My post-doc under the quantum critical dynamics of tensor networks grant has been collaborating with Prof Robert Konik to compare predictions of out of equilibrium quantum dynamics under cMPS and conformal field theory.
Collaborator Contribution Prof Robert Konik has committed both his time and the time of his post-doc to this research
Impact Publications expected shortly
Start Year 2015
 
Description British Association of Science Writers/UCL 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach Regional
Primary Audience Media (as a channel to the public)
Results and Impact Audience of about 50 science writers and post-graduate students. Talk about gravity/quantum correspondence and fluctuation stabilisation of new phases.
Year(s) Of Engagement Activity 2012
 
Description Discovery Magazine Interview 
Form Of Engagement Activity A press release, press conference or response to a media enquiry/interview
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Public/other audiences
Results and Impact Interview (several) with Discovery magazine for an article on the application of gravitational ideas to the understanding of quantum mechanics
Year(s) Of Engagement Activity 2015
 
Description Hobart High School Norwich - Talk 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach Regional
Primary Audience Schools
Results and Impact Talk to 2nd year high school students during day followed by talk to parents and 5th year students in evening. Fairly wide-ranging subject matter in quantum mechanics related to the idea of flucutation stabilised phases Lots of questions.
Year(s) Of Engagement Activity 2013
 
Description LIMS talk on AdSCFT and Gravity 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach Regional
Primary Audience Public/other audiences
Results and Impact A layman's presentation of the applications of ideas from general realtivity to the understanding of quantum mechanics.
Year(s) Of Engagement Activity 2015
 
Description Talk at Deutche Bank 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach Regional
Primary Audience Industry/Business
Results and Impact Talk on stability from fluctuations to financial analysts. About 50 physically present with approx 100 likely on company intranet. Interesting subsequent discussions and undergraduate MSc project.
Year(s) Of Engagement Activity 2015
 
Description UCL Science Lectures for Sixth Formers 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach Regional
Primary Audience Schools
Results and Impact About 200 sixth form students and a handful of the general public attended a talk on the role of fluctuations in stabilising unusual states of matter. Lots of questions were raised.
Year(s) Of Engagement Activity 2013