Hybrid quantum and classical computation: exploiting the best of both paradigms

Lead Research Organisation: Durham University
Department Name: Physics

Abstract

Digital electronic computation has become ubiquitous on a very rapid timescale: more and faster computation is in greater demand than ever. Quantum computing promises more raw computing power than we can achieve classically: turning this promise into reality is the overarching goal of my research. I will address the key theoretical issue that will enable us to fully exploit quantum computation: how to combine quantum and classical computation to gain maximum computational power and efficiency.

It is a crucial time to step up the development of quantum computing: Google recently bought their first "quantum computer". This device, from D-Wave (Burnaby, Canada), is solving real problems for commercial applications, even though we don't yet know whether it is actually exploiting quantum mechanics to achieve efficient computation beyond the reach of classical machines. Quantum computing is clearly coming of age: to ensure the UK has a place in the forefront of these developments we need our theorists and experimentalists to play their part in leading this computing revolution.

My research is central to the key questions the D-Wave quantum computer challenges us with.
How, exactly, do we persuade quantum systems to solve hard classical problems efficiently for us? We are part of the way there, we already know how to solve quantum problems: Feynman in 1982 first described how a quantum computer could efficiently simulate quantum systems, and experiments that can do this are well under way in labs around the world. Classical problems are tougher, there are relatively few algorithms promising a speed up.

To use a quantum computer to solve a classical problem, such as factoring large numbers, or searching a random data set, or finding the best solution under a complex set of constraints, or modelling a large system (climate or proteins for example), we need a hybrid classical-quantum device that can start with the classical problem, convert it into a quantum representation, solve it, and then return the solution as classical data. Existing theoretical models of computation are simple, elegant, single paradigm models that perform well for analysis of complexity and computability - how hard it is to solve, and what are the minimum resources required - but methods of combining different models into hybrid composites that more closely match real computational devices are missing.

Even the simplest experimental quantum processor is a hybrid device, typically combining classical controling hardware with two or more different quantum systems interacting through precisely specified sequences of operations. Hybrid quantum systems enable more practical experiments and more efficient quantum computer programs, both of which are essential to reduce the noise that would otherwise render quantum devices useless. But we don't yet know what is the best model of computation we should use to physically build useful computers. Silicon-based digital technology is serving us well, but the bienniel doubling of classical computing power is reaching quantum limitations in how small the elemental components can be made, and a diversity of less conventional devices are invading the marketplace for our daily productivity and entertainment. Niches are opening up for many special purpose types of computer, of which quantum is one important example.

I will address these key gaps in our knowledge by developing a theoretical understanding of composite quantum-classical computational devices with real-world constraints applied, and by detailed theoretical and computational modelling of hybrid quantum-classical systems to characterise their properties, computational power and the conditions required for their efficient operation. This will enable me to provide the science and leadership that will place the UK in a prime position to produce and exploit the technology in the new era of quantum computation.

Planned Impact

During the project, the beneficiaries will all be academic as detailed in the "Academic Beneficiaries" section. The most important of these will be the ICT research community, who will be able to use the results from my research to embed quantum processors into their designs for new computational architectures. I have provided a work package in the "Pathways for Impact" section to encourage the ICT community to become actively involved in this research. The workshops will provide opportunities to form new collaborations, and the speaker tours will bring in expert knowledge from outside the UK.

The Physical Sciences community will also benefit from my results which will be useful for development of special purpose quantum simulators, and for quantum computational devices more generally. Theorists in ICT, Mathematics and Physical Sciences will all be able to use my results on the computational power of non-Turing-Universal quantum devices to extend their own work in this and related areas.

The two PDRAs will benefit from training in interdiscipinary quantum information science, as one would expect, moreover, they will also be in a prime position to lead the theory part of any spin-out companies after the end of the project, or for a company who starts to develop quantum devices. This is not a role I want for myself, so training suitable PDRAs who could take this role is important for future impact.

In the medium term, up to five years after the end of this project, in addition to continuing relevance to the academic communities outlined above, the development of quantum computational devices will begin to be commercialised as a result of further development from my theoretical pointers for practical devices. This will thus be a benefit for industry who choose to invest in such development, and as products appear, for the users, who will initially be in areas requiring fast processing power, either for real time applications or for sheer processing power of a type the new devices can provide. These could be in complex optimisation problems, or in numerical modelling in areas as diverse as biomedics for drug discovery, or climate prediction.

In the long term, this research will lead to the emergence of an industry sector providing quantum computation. This will consist of both device manufacturers, producing modules that are embedded in general purpose computers, and cloud computing service providers, with central server farms of quantum processors accessed using secure quantum communications, which will also develop alongside quantum computation (is in fact currently further advanced). This will enable access to the processing power provided by quantum computers for all who may be have need of it for whatever computational tasks they require, be they individuals, small or large companies, public sector, education and research. The largest users could even turn out to be the entertainment sector for online real time processing; the availability of faster computation has always driven applications beyond those initially envisioned. However, the economic benefits of leading in this industry sector as it grows will accrue to the UK whoever the users turn out to be.

Publications

10 25 50
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Barnett S (2017) Journeys from quantum optics to quantum technology in Progress in Quantum Electronics

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Bougroura H (2016) Quantum-walk transport properties on graphene structures in Physical Review A

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Callison A (2019) Finding spin glass ground states using quantum walks in New Journal of Physics

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Chancellor N (2016) An Overview of Approaches to Modernize Quantum Annealing Using Local Searches in Electronic Proceedings in Theoretical Computer Science

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Chancellor N (2021) Experimental test of search range in quantum annealing in Physical Review A

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Chancellor N (2017) Modernizing quantum annealing using local searches in New Journal of Physics

 
Description (1) several types of new methods for using quantum systems as computers, that are very different from digital computing. These allow early quantum computers to make best use of expensive resources, thus maximising the computation they can provide. (2) methods to adapt classical error correction codes to improve error correction for quantum devices. (3) methods for designing hybrid quantum-classical algorithms for quantum annealers (a type of quantum computer) that use the best known classical algorithms augmented by a quantum subroutine to provide extra processing power.
Exploitation Route Experimental quantum technology can use these ideas to build more powerful quantum computers. More efficient algorithms for early quantum computers can provide useful quantum computing sooner on imperfect hardware. The algorithms have a very wide range of applications to solve optimisation problems, some of which I have indicated by the tick box sectors.
Sectors Aerospace, Defence and Marine,Digital/Communication/Information Technologies (including Software),Electronics,Energy,Financial Services, and Management Consultancy,Healthcare,Manufacturing, including Industrial Biotechology,Pharmaceuticals and Medical Biotechnology,Transport

URL https://www.dur.ac.uk/qlm/research/quantumtech/structured-devices/
 
Description 1) D-Wave Inc. have been inspired by methods in papers by my PDRA Dr Nicholas Chancellor to implement extra controls on their quantum systems to enable reverse annealing to be performed. 2) Expertise gained through fellowship has led to the PI serving on policy bodies including BEIS Expert Group on Quantum Computing, the House of Lords Science &Technology Committee (provided evidence on quantum technology), EPSRC Strategic Advisory Teams (ICT and e-Infrastructure). Through this, the PI is using her expertise to shape future policy and investment in quantum computing and high performance computing capability in the UK.
First Year Of Impact 2017
Sector Aerospace, Defence and Marine,Digital/Communication/Information Technologies (including Software),Education,Government, Democracy and Justice,Other
Impact Types Economic,Policy & public services

 
Description CCP-QC: Collaborative Computational Project - Quantum Computing
Amount £163,421 (GBP)
Funding ID EP/T026715/1 
Organisation Engineering and Physical Sciences Research Council (EPSRC) 
Sector Public
Country United Kingdom
Start 03/2020 
End 03/2025
 
Description Durham University EPSRC Impact Acceleration Account (IAA) Programme
Amount £13,855 (GBP)
Organisation Durham University 
Sector Academic/University
Country United Kingdom
Start 10/2018 
End 12/2019
 
Description EPSRC Hub in Quantum Computing and Simulation
Amount £23,960,280 (GBP)
Funding ID EP/T001062/1 
Organisation Engineering and Physical Sciences Research Council (EPSRC) 
Sector Public
Country United Kingdom
Start 12/2019 
End 11/2024
 
Description NQIT Quantum Technology Hub Partnership Funding
Amount £20,298 (GBP)
Organisation University of Oxford 
Sector Academic/University
Country United Kingdom
Start 10/2018 
End 11/2019
 
Description Quantum Enhanced and Verified Exascale Computing - QEVEC
Amount £1,007,642 (GBP)
Funding ID EP/W00772X/2 
Organisation Engineering and Physical Sciences Research Council (EPSRC) 
Sector Public
Country United Kingdom
Start 08/2021 
End 08/2024
 
Description D-Wave Systems Inc 
Organisation D Wave Systems
Country Canada 
Sector Private 
PI Contribution Testing hybrid quantum-classical algorithms on D-Wave Systems, using newly added features of reverse annealing.
Collaborator Contribution Implemented the reverse annealing features proposed in publication by PDRA
Impact Presentation at conferences: AQC 2018, and D-Wave European Users meeting 2018
Start Year 2018
 
Description Simula Research Laboratory, Norway 
Organisation Simula Research Laboratory
Country Norway 
Sector Academic/University 
PI Contribution Expertise in quantum computing to support a successful funding application, through which future collaboration will be supported.
Collaborator Contribution Successful funding application: "Future Ubiquitous Services and Data with Dependable Quantum Programs (Qu-Test)" under the Research Council of Norway IKTPLUSS "Ubiquitous data and services" call. Project starts April 2020 so no further results to report yet. Expect to receive travel funding to support visits for collaboration, but don't yet know the value of this.
Impact None yet, just starting.
Start Year 2019
 
Description HPC&Q Invited talk 5th Feb 2019 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Industry/Business
Results and Impact Invited talk at conference in QE II Centre on Hybrid Quantum and Classical Computing
over 300 people in audience from industry, academia, journalists, funders, and politicians
has led to further invitations to present to wider audiences
feedback indicated many found the talk useful and interesting
Year(s) Of Engagement Activity 2019
URL https://ukhpc.co.uk/
 
Description IoP Schools talk Nottingham 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach Regional
Primary Audience Schools
Results and Impact 6th form pupils from Nottingham schools attended my talk on quantum computing held on the Nottingham University campus. Good range of questions and positive feedback from pupils at end of talk. Alternative URL http://www.nottingham.ac.uk/physics/outreach/nottingham-physics-centre.aspx (can only enter one URL below).
Year(s) Of Engagement Activity 2015
URL http://www.iop.org/activity/branches/calendar/index.html?trumbaEmbed=view%3Devent%26eventid%3D115697...
 
Description LMS CS Colloquium 18 Nov 2018 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach Regional
Primary Audience Postgraduate students
Results and Impact Invited talk at the London Mathematical Society Computer Science Colloquium on 18th November 2018
Aimed at masters and PhD level students, the audience was actually a bit broader, approx 60 people
Discussions in breaks indicate interest and appreciation of the talk.
Year(s) Of Engagement Activity 2018
 
Description Talk IET East Midlands branch (Derby) 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach Regional
Primary Audience Professional Practitioners
Results and Impact General interest talk on quantum computing to regional IET meeting. Note that Derby has many Rolls Royce employees who showed keen itnterest in the topic through questions and discussion afterwards.
Year(s) Of Engagement Activity 2016
 
Description Talk for local IET group (Shrewsbury) 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach Regional
Primary Audience Public/other audiences
Results and Impact Return visit a year later (they liked my talk on quantum computing so much) to give talk on quantum cryptography and security in a quantum world to IET Shropshire regional group. Attended by over 40 members, with some follow up emails indicating real interest in the topic.
Year(s) Of Engagement Activity 2018
URL http://www.theiet.org/events/local/250608.cfm?nxtid=
 
Description Talk for local IET group (Warwick) 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach Regional
Primary Audience Industry/Business
Results and Impact Public outreach talk on quantum computing to regional IET group in Warwickshire. Well-attended by a range of members young to old, many from the automobile industry. Also attended their AGM dinner and talked with members about quantum technology and other topics.
Year(s) Of Engagement Activity 2017
URL http://www.theiet.org/events/local/249471.cfm?nxtid=
 
Description Talk to IET Shropshire regional branch (Shrewsbury). 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach Regional
Primary Audience Public/other audiences
Results and Impact General interest talk on quantum computing to very varied audience of engineers, retired to school students and their friends. Lively interest in questions and discussion after the talk, and school students asking for university information.
Year(s) Of Engagement Activity 2017