Publications

General Articles

1. Quantum Systems Engineering: A structured approach to accelerating the development of a quantum technology industry
   M.J. Everitt, Michael J de C Henshaw, Vincent M Dwyer
   
   Invited contribution to 18th International Conference on Transparent Optical Networks ICTON 2016 (topic: quantum photonics).
   
   Discussion paper (four pages, no figures, perspectives/opinion piece - does not contain new scientific findings)
   
   The exciting possibilities in the field of new quantum technologies extend far beyond the well-reported application of quantum computing. Precision timing, gravity sensors and imagers, cryptography, navigation, metrology, energy harvesting and recovery, biomedical sensors and imagers, and real-time optimisers all indicate the potential for quantum technologies to provide the basis of a technological revolution. From the field of Systems Engineering emerges a focused strategy for the development cycle, enabling the existence of hugely complex products. It is through the adoption of systems thinking that the semiconductor industry has achieved massive industrial and economic impact. Quantum technologies rely on delicate, non-local and/or entangled degrees of freedom - leading to great potential, but also posing new challenges to the development of products and industries. We discuss some of the challenges and opportunities regarding the implementation of Systems Engineering and systems thinking into the quantum technologies space.
   
   

2. Towards A UK Co-Operative For the Advancement of Quantum Technology
   A Report on the Outcomes of the DSTL Defence & Security Quantum Community Meeting, September 2015 Loughborough University, UK - a contribution to the UK National Quantum Technology Programme

   Kieran Bjergstrøm, Trevor Cross, Vincent Dwyer, Mark Everitt, Michael Henshaw, Paul John, Jack Lemon, Leon Lobo, Richard Murray, Doug Paul, Jonathan Pritchard, Jason Ralph, Stephen Till, Craig Wrigley

   Published onliine, October 2016: DOI: 10.13140/RG.2.2.36739.09766

   The meeting was the fourth in DSTL’s series of community meetings and had a Systems Engineering theme – recognising the increasing importance of this topic for many in the Quantum Technology (QT) community. There is a growing recognition that, although there are significant research challenges associated with realising the commercial and societal benefits anticipated from quantum technologies, there are also other challenges which concern the physical, commercial, societal and regulatory environments into which these new technologies will be integrated.
   
   This document reports on discussions held at the meeting around this question and, leveraging this input, seeks to provide clear and appropriate recommendations to the UK QT community.
   

Journal Articles

1. Wigner Functions for Arbitrary Quantum Systems [arxiv] Phys. Rev. Lett. 117, 180401 (2016)
   Todd Tilma, M.J. Everitt, J.H. Samson, William J. Munro, Kae Nemoto
   
   The possibility of constructing a complete, continuous Wigner function for any quantum system has been a subject of investigation for over 50 years. A key system that has served to illustrate the difficulties of this problem has been an ensemble of spins. While numerous attempts have come close to generating a complete Wigner phase-space description, each has either being artificial in its construction or fallen short of realising this ambition. Here we present a natural method of constructing Wigner functions that can be used to fully describe any quantum object or systems of systems. We see no reason why our approach should be limited to non-relativistic quantum mechanics; it may even lead to phase-space methods for more exotic frameworks such as string theory. In addition we show that the natural visual representation of the quantum state by the Wigner function leads to multiple and intuitive entanglement measures.
   
   
2. Some implications of superconducting quantum interference to the application of master equations in engineering quantum technologies [arxiv] Phys. Rev. B 94, 064518 (2016)
   S. N. A. Duffus, K. N. Bjergstrom, V. M. Dwyer, J. H. Samson, T. P. Spiller, A. M. Zagoskin, W. J. Munro, Kae Nemoto, and M. J. Everitt
   
   In this paper we consider the modeling and simulation of open quantum systems from a device engineering perspective. We derive master equations at different levels of approximation for a superconducting quantum interference device (SQUID) ring coupled to an ohmic bath. We demonstrate that the master equations we consider produce decoherences that are qualitatively and quantitatively dependent on both the level of approximation and the ring's external flux bias. We discuss the issues raised when seeking to obtain Lindbladian dissipation and show, in this case, that the external flux (which may be considered to be a control variable in some applications) is not confined to the Hamiltonian, as often assumed in quantum control, but also appears in the Lindblad terms.
   
   
3. On the quantum‐to‐classical transition of a particle in a box
   JE Paton, MJ Wootton, MJ Everitt
   Annalen der Physik
    
   Anyone who plays snooker, billiards or pool will be familiar with the way in which classical particles bounce off walls. For certain shaped tables these trajectories become chaotic. Quantum particles behave in a very different way. We seek to understand how the everyday classical behaviour of billiards can arise in a world that is fundamentally quantum and how we might experimentally study this phenomena in nano-mechanical systems.
    
   Undersanding the quantum to classical transition is important not only for the foundations of quantum mechanics but also necessary for establishing the point at which quantum phenomena can be neglected. considerations of this area of study will be very important when developing an understanding of complex quantum systems and technologies based upon them.
    
4. Engineering Dissipative Channels for Realizing Schrödinger Cats in SQUIDs
   MJ Everitt, TP Spiller, GJ Milburn, RD Wilson, AM Zagoskin
   Front. ICT, Quantum Computing 1, 1
    
   The effects of the environment on quatum devices is usually considered to have a detrimental effect. In this work we look at using specially engineered environments to do the opposite - namly making a device more quantum mehanical than it would be without the environment being present. This can be thought of as first steps towards engineering for reliability in quantum technologies.