Synthesis of Quantum States

Microelectronics and lasers, two of the major technologies underpinning the information age, are but comparatively rudimentary applications of the theory of Quantum Mechanics. A major drive of current research is to realise the full potential of a fully quantum-derived information age.

One framework to express these futuristic technologies is Quantum Information, which describes their operation simply in terms of an underlying quantum state, and manipulations that have to be performed on it. Different quantum states yield different protocols.

Existing protocols rely on only a very small set of states, and much experimental effort is expended in producing high quality versions of these states. However, production is often specified in terms of a complex sequence of operations. In this research, we will study a more natural production method wherein the synthesis of an appropriate quantum state is embedded in the natural properties of the system. This will mean that future experiments, aimed at building new quantum technologies, will be able to initialise themselves with minimal experimental effort, and in an easily repeated way.
This technique is already known to work in specific situations (known as "Perfect state transfer"), and has already been experimentally implemented. Our task is to extend this special case into a broader concept that can be applied to any quantum information protocol. In practice, this means concentrating on the production of those small number of specific states that most protocols are based on, but also means that a characterisation of the states that can be produced can drive new theory - if we produce a particular state, what can be done with it?

This theoretical concept could facilitate a far more rapid adoption of quantum technologies than would otherwise be possible. Specifying a desired functionality is one thing; laboratory realisation is another due to the manifold external influences collectively known as noise or decoherence. These corrupt the perfect concept, meaning that the final product is not the desired one. The final part of this project will study how those effects may be mitigated through the use of further engineering of the system, and by encoding the desired functionality into a form of error correcting code. Ultimately, the hope is that this decoherence might be used to engineer a difference range of states from those which one would be able to access without it, turning unwanted aspect into an essential feature.

As a theoretical study in Quantum Information Processing, the most direct impact of the proposed research will be on academic beneficiaries. Indeed, the purpose of the research is to facilitate experimental realisations of quantum technologies by reducing the technical demands on an experiment, concentrating on the properties of the experiment that are most easily controlled, and working around those that aren't. With EPSRC's Quantum Technology Hubs in place to provide the framework to accelerate the evolution of these experiments into real-world applications with genuine societal and economic impact, these academic beneficiaries will mediate the medium to long-term impact of the work. An extraordinary diversity of hugely influential impacts is anticipated for these new quantum technologies, and those will not be realised by individuals; they will arise as part of a coordinated strategy to which this research will contribute at a conceptual level.