Device Independent Quantum Information Processing
Lead Research Organisation:
University of Oxford
Department Name: Computer Science
Abstract
Device-Independent Quantum Information Processing represents a new paradigm for quantum information processing: the goal is to design protocols to solve relevant information tasks without relying on any assumption on the devices used in the protocol. For instance, protocols for device-independent key distribution aim at establishing a secret key between two honest users whose security is independent of the devices used in the distribution. Contrary to standard quantum information protocols, which are based on entanglement, the main resource for device-independent quantum information processing is quantum non-locality. Apart from the conceptual interest, device-independent protocols offer important advantages from an implementation point of view: being device-independent, the realizations of these protocols, though technologically challenging, are more robust against device imperfections. Current and near-future technology offer promising perspectives for the implementation of device-independent protocols.
This project explores all these fascinating possibilities. Its main objectives are (i) obtaining a better characterization of non-local quantum correlations from an information perspective, (ii) improve existing and derive new application of this resource for device-independent quantum information processing and (iii) design feasible implementations of device-independent protocols. We plan to tackle these questions with an inter-disciplinary approach combining concepts and tools from Theoretical and Experimental Physics, Computer Science and Information Theory.
This project explores all these fascinating possibilities. Its main objectives are (i) obtaining a better characterization of non-local quantum correlations from an information perspective, (ii) improve existing and derive new application of this resource for device-independent quantum information processing and (iii) design feasible implementations of device-independent protocols. We plan to tackle these questions with an inter-disciplinary approach combining concepts and tools from Theoretical and Experimental Physics, Computer Science and Information Theory.
Planned Impact
See attached proposal.
Organisations
People |
ORCID iD |
| Jonathan Barrett (Principal Investigator) |
Publications
Allen J
(2017)
Quantum Common Causes and Quantum Causal Models
in Physical Review X
Bancal J
(2013)
Definitions of multipartite nonlocality
in Physical Review A
Barnum H
(2015)
Entropy, majorization and thermodynamics in general probabilistic theories
in Electronic Proceedings in Theoretical Computer Science
Barrett J
(2014)
No ?-epistemic model can fully explain the indistinguishability of quantum states.
in Physical review letters
Barrett J
(2013)
Memory attacks on device-independent quantum cryptography.
in Physical review letters
Horsman C
(2014)
When does a physical system compute?
in Proceedings. Mathematical, physical, and engineering sciences
Lee C
(2015)
Computation in generalised probabilisitic theories
in New Journal of Physics
Lee CM
(2016)
Bounds on the power of proofs and advice in general physical theories.
in Proceedings. Mathematical, physical, and engineering sciences
Masanes L
(2014)
Full Security of Quantum Key Distribution From No-Signaling Constraints
in IEEE Transactions on Information Theory
Nigg D
(2015)
Can different quantum state vectors correspond to the same physical state? An experimental test
in New Journal of Physics
| Description | Since the early days of quantum theory, it has been known that quantum systems can exhibit phenomena that defy any intuitive understanding. But it is only over the last twenty years or so that researchers have realized how to harness these strange phenomena for powerful kinds of information processing. The aim of the research was to develop a quantitative understanding of some of the distinctively non-classical features of quantum theory, to develop a theory of causal inference appropriate to scenarios involving quantum systems, and to develop a theory that explains how certain physical properties of systems described by a theory are related to information-processing power. An important property of quantum states, underlying the success of various important protocols, such as quantum cryptography, is that given two distinct quantum states it is not always possible to determine which is which. This would be natural if a quantum state merely expresses imperfect knowledge of some underlying reality. One key finding was that the quantitative statistics of quantum measurement outcomes are incompatible with this view. In addition to the theoretical work, we collaborated with an experimental team based in Innsbruck, led by Rainer Blatt, who performed the relevant quantum measurements on trapped ions. The experiment verifies quantum predictions to a very high precision. A framework of quantum causal modelling was developed, enabling a precise description of the causal relationships that obtain between different quantum systems, and of how these relationships can be inferred from observed data. This is important, e.g., for characterising the noise that is present in realistic quantum devices, or for verifying that quantum devices are behaving as they should. Finally, we considered the relationship between the physics of a system and computational power. We introduced the concept of computation using devices that are characterized operationally, rather than having a given quantum description. We showed that a rigorous computational model can be defined, which makes it possible to characterize the class of problems that can be solved efficiently using a given set of devices. We were able to derive an upper bound on the power of a computer, given only the assumption that a principle related to spacial locality is obeyed. This bound can be seen as a fundamental limit on computational power that follows from the basic structure of how devices behave. |
| Exploitation Route | Our proof that quantum statistics are incompatible with a view in which quantum states express imperfect knowledge of an underlying reality has been developed by other researchers. This has led to increasingly compelling demonstrations of this non-classical aspect of quantum theory, and various experimental teams have reported corresponding experiments. Other researchers have used the results as a basis for quantum protocols in which information theoretic tasks are achieved that are impossible with classical systems. Our understanding of the power of quantum computers is in its infancy, with the very great interest in quantum computers spurred by only a handful of known problems for which they seem to be faster than classical computers. There is very little existing knowledge on the connections between the structure of a physical theory, and the power of computers governed by that theory, and our work represents only a first step in this direction. We are currently working on taking our findings forward by describing the class of general physical theories that a quantum computer would be able to simulate efficiently. In addition to a better understanding of fundamental questions, this will lead to a new approach to the design of quantum algorithms. The framework for quantum causal modelling has been used by many other researchers, and used, for example, to find quantum advantages for computational and communication tasks. The work also provided new insights into causal reasoning in scenarios without quantum systems -- that is, causal reasoning about classical variables, which may represent the data gathered by autonomous AI systems, or in medical trials. This is currently a major area of investigation, by both university academics and companies. |
| Sectors | Digital/Communication/Information Technologies (including Software),Other |
| Description | The development of a framework for quantum causal modelling led to new insights into causal reasoning in situations without quantum systems, i.e., involving only classical data. Two PhD students involved with the project have now moved into the private sector, where they are applying these results, and the skills that they learned, to real world problems. One works with Babylon, a company who amongst other things are developing AI systems for improved medical diagnosis. The other works for Wayve, a company developing self-driving cars. |
| First Year Of Impact | 2018 |
| Sector | Digital/Communication/Information Technologies (including Software),Healthcare,Transport |
| Impact Types | Societal,Economic |
| Description | ERA-Net CHIST-ERA -- Device Independent Quantum Information Processing |
| Amount | £91,722 (GBP) |
| Funding ID | EP/J008249/1 |
| Organisation | Engineering and Physical Sciences Research Council (EPSRC) |
| Sector | Public |
| Country | United Kingdom |
| Start | 02/2013 |
| End | 07/2015 |
| Description | FQXi Large Grant -- Thermodynamic vs information theoretic entropies in probabilistic theories |
| Amount | £73,279 (GBP) |
| Organisation | Foundational Questions Institute (FQXi) |
| Sector | Charity/Non Profit |
| Country | United States |
| Start | 09/2013 |
| End | 08/2015 |
| Description | Quantum Causal Structures |
| Amount | $2,601,946 (USD) |
| Funding ID | 60609 |
| Organisation | The John Templeton Foundation |
| Sector | Academic/University |
| Country | United States |
| Start | 12/2016 |
| End | 08/2019 |
| Description | UK National Quantum Technologies Programme -- Oxford Quantum Hub |
| Amount | £40,000,000 (GBP) |
| Funding ID | EP/M013243/1 |
| Organisation | Engineering and Physical Sciences Research Council (EPSRC) |
| Sector | Public |
| Country | United Kingdom |
| Start | 12/2014 |
| End | 12/2019 |
| Description | Ars Technica |
| 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 | Media (as a channel to the public) |
| Results and Impact | I was interviewed by a journalist, who was preparing an article for the popular website Ars Technica. The article describes research of mine, including a new theorem that I published in collaboration with other researchers from Oxford, and the University of Sydney. |
| Year(s) Of Engagement Activity | 2014 |
| URL | http://arstechnica.com/science/2014/07/quantum-state-may-be-a-real-thing/ |
| Description | Economist article |
| 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 | Media (as a channel to the public) |
| Results and Impact | Interviewed by a journalist for an article on quantum cryptography that appeared in The Economist. |
| Year(s) Of Engagement Activity | 2013 |
| URL | http://www.economist.com/news/science-and-technology/21586529-quantum-cryptography-has-yet-deliver-t... |
| Description | Oxford science blog |
| Form Of Engagement Activity | A press release, press conference or response to a media enquiry/interview |
| Part Of Official Scheme? | No |
| Geographic Reach | National |
| Primary Audience | Public/other audiences |
| Results and Impact | I was interviewed by a journalist writing for the Oxford Science Blog, run by the University of Oxford. The article "Counting Quantum Cards" reports a new theorem that I published, in collaboration with other researchers from Oxford and the University of Sydney. |
| Year(s) Of Engagement Activity | 2014 |
| URL | http://www.ox.ac.uk/news/science-blog/counting-quantum-cards |