InSb Quantum Devices: All-electrically Controlled Electron Spins. (ACES)

Despite challenges with decoherence, solid state spin qubits remain one of the best practical implementations of quantum device architectures that exploit quantum state entanglement, owing to the possibility of incorporation into existing electronics technology. 'Physics for Quantum Technologies' was acknowledged in a recent EPSRC Physics Grand Challenge survey as the most overwhelmingly recognised challenge in the physical sciences. "New materials for solid-state quantum electronics need to be developed" was a highlighted high level requirement. Physics for Quantum Technology was also acknowledged as having the highest potential UK economic impact should the UK establish an intellectual advantage.

All electrical control of single electron spins in a practical semiconductor device would be a major breakthrough which the UK is in a unique position to achieve owing to the world lead it has in the strong spin-orbit InSb/AlInSb semiconductor material system. There are a number of key stepping stones to achieving the end goal of single electron manipulation in gate confined quantum structures. We propose to address the material growth challenges of highly mismatched InSb/InAlSb epitaxy on GaAs and Si, and achieve world record carrier mobilities and associated ballistic length, and develop device capability for advanced measurement and exploitation by the wider UK scientific community.

Through a series of standard quantum transport devices, this work will ultimately demonstrate the potential for electron spin manipulation (and therefore individual qubit addressing) by the spatial translation of single electrons in complex multiple gate field effect devices, using the Rashba spin-orbit coupling to enable local spin state control.

The long term societal impact of the quantum information revolution cannot be understated. Even before practical processors are available to engineers and entrepreneurs, the field has identified major applications that would present significant opportunity or major disruption to present day life, some with only the availability of a limited number of quantum bits (qubits). Whilst the threat posed by the breaking of public key encryption has been significant enough to generate large funding in the US, EU and Japan, the opportunities arising from this technology potentially eclipse this. The ability to search mass cctv footage using pattern recognition algorithms that exploit the quantum fourier transform, might one day yield almost real time UK wide search and surveillance, impacting how we think about and coordinate national security, missing persons, crime prevention, facility and infrastructure monitoring etc. Quantum algorithms that solve problems in physics and chemistry will have a major impact on complex system design, such as drug design simulation, leading to greater efficiency in chemical and pharmaceutical manufacturing. However achieving breakthroughs in technology will take sustained effort and must play to UK strengths.

Novel devices that rely on electron spin have been shown to be promising candidates for simple qubit and quantum state study. Only two groups worldwide have reported any form of quantum devices using high mobility 2DEG material based on InSb/AlInSb heterostructures (QinetiQ Malvern (UK), and Oklahoma (US)), and yet there are considerable advantages associated with the large spin-orbit interaction. Now that QinetiQ has withdrawn from this field there are a number of active groups (Imperial (Cohen, Gilbertson), Oxford (Nicholas), Surrey (Murdin, Clowes)) that will not pursue this work without a quality material supply and underpinning device knowledge. The barriers to progress in this material system are significantly lower for the UK owing to this work.

Recent market analysis has put the global market value for quantum enabled technology devices to be ~$410bn by 2015, with a compound annual growth rate of ~39%. The extent to which UK Industry can benefit is difficult to estimate given the potential breadth of applications and differing levels of market presence. Taking the ICT sector alone, the UK electronics industry generated approximately £16BN ($24bn) of output in 2006. This would give the UK an approximate 7% share of the current global market (excluding micro-processors) for electronics and electrical systems. Applying this market share to the future market for quantum technology, the estimated sales to UK producers (from UK and international markets) would be between £9BN and £23BN.

Specialist skills developed in this project are essential in any future high technology exploitation chain, and are sought after by industries that use such controlled environment (cleanroom) laboratories (ranging from semiconductor devices to advanced drug research). This project will drive forward complex semiconductor device concepts and in the process train PhD students and postdoctoral level workers in advanced, novel, and creative nano-device fabrication and measurement. There will be excellent opportunity for high profile publication and presentation for early career workers.
The UK must contribute to this field with a unique angle and not simply duplicate multi-billion pound investments made elsewhere in the world, notably in America, Japan and continental Europe. The UK has the infrastructure and in depth expertise in III-V technologies, together with specialist knowledge gained from years of MoD and commercial investment to lead the world in InSb technology. This brings to the table a significant 'slant' on the realisation of solid state spin qubits with advantages for practical realisation and long term commercialisation.