Harnessing the interface between silicon and its thermal oxide has had, and continues to have, enormous impact on humankind through the crucial role it plays in metal-oxide-semiconductor transistors. These transistors can be found in anything containing integrated circuitry like computers. Due to the importance of this interface, vast efforts were made to understand the underlying physics around three decades ago and as such, it is often assumed that most of the pertinent physics is well understood.However, along with extreme miniaturisation and the developing interest in quantum information processing, we are now entering into an exciting new era where our understanding of silicon is tested in ways only dreamt about thirty years ago. Miniaturisation has come so far, that cross-sectional micrographs of cutting-edge transistors can now show individual atomic structures on the same picture encompassing an entire device. In such small devices, and indeed in emergent devices aimed at manipulating quantum information, details such as atomic layer fluctuations of an interface and quantum mechanical effects come to the fore. These have enormous effects on device properties, rendering further progress critically dependent on our ability to understand and control them. This is leading to a world-wide revival of interest in the basic physics of silicon. As an unexpected and surprising result of this endeavour, recent experiments have revealed, that when the interface is prepared in a particular manner, the band-structure of silicon is profoundly altered in a completely new way which we call giant valley-splitting . The band-structure of a material lies at the very heart of the physics of any crystalline solid - it dictates all properties involving electrons such as how suitable the material is for use in a transistor, and what colour of light the material absorbs and emits.Despite silicon-silicon dioxide being one of the most important interfaces in the infrastructure of modern society, at present, we know very little about this effect. We do not have a quantitative theory to explain it; we do not know what microscopic structural parameters determine it; we do not know what exact preparation parameters determine it, and we do not know how it affects other physical properties except limited aspects of electrical conductivity. In this respect, this silicon-silicon dioxide interface is a new material with yet-unknown properties.The aim of this project is to understand the origin and consequences of this new interface so that we can harness it as a new ingredient for physics of low dimensional systems and technology of semiconductor devices. Since the material is made from silicon and silicon dioxide, it is automatically compatible with the vast arsenal of cutting-edge silicon technology. New properties and resulting functionalities can be embedded into existing silicon based systems at the deepest level of integration which is impossible with any other material.

Quantum information technology seeks to encode bits and bytes of information onto microscopic quantum systems. Governed by quantum mechanics, these systems can be in superposition, can interfere, and entangle, revolutionising devices which collect data, communicate, and compute. Future quantum sensors will measure with precision beyond the classical shot-noise limit; quantum transceivers will fundamentally guarantee security and detect eavesdroppers; and quantum computers, the most ambitious of quantum devices, will tremendously accelerate certain calculations. Photons, quanta of light, have several attractive properties: they travel, allowing information to move quickly within and between devices; they are low noise, crucial for low error rates; and they are the quantum system for which, through 1000 years of optics, we have developed the best intuition and the most mature technology. Despite this, optical elements-lenses, mirrors, shutters, beamsplitters, crystals-perform too poorly, and are too bulky and manual, for example, to put quantum sensors in a smartphone, or to build quantum computers with millions of elements. Photon-photon interactions naturally depend on chance, but new ideas suggest clever control systems can inject certainty. Crucially required are: optical switches, electronics, and single-photon detectors. For success, all these elements must be integrated and delivered at scale. Scalability-the ability to increase complexity without limit-is what photonics has so far lacked, in both size and performance. To achieve large-scale quantum computation with photons or the large-scale deployment of devices for optical quantum sensing and communication-to make quantum photonics useful-it must scale up. This programme will critically re-engineer quantum photonics for scale. It will build a platform from which fantastic quantum devices can be launched, and it will launch them. Silicon electronics is now ubiquitous, with high performance and extreme complexity. Silicon photonics has followed on its coat-tails, with microscopic optical elements, huge wafers, global manufacturing, and unrivalled know-how. In recent years, silicon photonics has grown into a huge research activity and a multi-billion-pound industry. This has propelled compact silicon quantum photonics, pioneered by the fellow, into unprecedented quantum complexity and functionality. In quantum optics, to lose a single photon is to lose irreplaceable quantum information. Silicon photonics is compact, but far too lossy: surface roughness and two-photon absorption are the main culprits. Light with long wavelengths, in the mid-infrared, however, can dodge both mechanisms, and pass with very little loss. In silicon, long-wavelength light is also more nonlinear, and optics for it are easier to make. This fellowship will combine the compactness and performance of silicon electronics and silicon quantum photonics to achieve high complexity and manufacturability, with performance enhanced by mid-infrared quantum optics and new technologies. By cleverly integrating very cold single-photon detectors (and so making the electronics and photonics very cold too) a quantum photonics platform for scale will be built. The fellow and his team, with help from collaborators, will pursue five objectives towards this aim: (1) to develop an ultra-low-loss chip optics platform based on mid-infrared silicon photonics, with low-loss fibre-chip couplers and delay lines; (2) to develop an ultra-fast, low-temperature, silicon-based electronic controller to dispense with chance; (3) to develop suitable fast and low-power electronic-to-optical interfaces; (4) to develop the infrastructure to do this at low temperatures; and (5) to launch fantastic quantum devices from the assembled platform.

The aim of this project is to realize a world-first Si-based integrated single-spin quantum bit (qubit) system on ultrathin silicon-on-insulator (SOI). We develop a precisely-controlled single-electron transfer technique to initialize truly single-electron spin (single-spin) states, micro electron spin resonance (micro-ESR) for single-spin manipulation, and a 'spin-to-charge' conversion technique for readout. These challenging technical requirements will be met by synergistically combining the expertise of the University of Southampton on cutting-edge silicon-based nanofabrication and single-electron devices, the University of Cambridge and the Hitachi Cambridge Laboratory on solid-state qubits and the associated low-temperature & RF measurements, and the NTT Basic Research Laboratories on single-electron / spin control technology.The first Si-based qubit was proposed by Kane using nuclear spins of phosphorous donor atoms in Si (Si:P qubits). This proposal attracted much interest due to the very long decoherence time of nuclear spins in Si. However, challenging bottom-up nanotechnologies, e.g. STM lithography, are required to control the number and position of P atoms embedded in silicon relative to surface control gates. Rather than using donors, which are atomic-like species, it is also possible to confine electrons in nano-fabricated structures known as quantum dots (QDs). An exquisite degree of control over single-electron spins (single-spins) has been demonstrated in QDs made from gallium arsenide. Unfortunately gallium arsenide is a nuclear spin rich environment leading to a rapid loss of coherence from electron spins. Recently, QDs capable of confining few electrons have also become feasible in silicon based materials, which have a low nuclear spin density, therefore providing a motivation for this research proposal. The recent appearance of isotopically pure Si materials (28Si 99.9%) also works in favour of Si-based systems by further increasing spin decoherence time. In order to develop the Si-based integrated single-spin qubit system, which has never been achieved, we fully exploit the unique set of state-of-the-art nanotechnologies brought together in our project team. Firstly, single-electron turnstile technology is adopted in order to prepare the well-defined initial single-spin states. Secondly, a high-speed charge detection technique is introduced using the radio-frequency single-electron-transistor (RF-SET). Thirdly, the detection of a single-spin state is realized based on the spin-to-charge conversion method. We propose a revolutionary SOI-based technology platform for integrated single-spin qubits, which features double single-spin turnstile devices (SSTDs) built as two parallel SOI-nanowires (SOINWs) with their edges interconnected by another short SOINW. The SSTDs are co-integrated with three other key components: (1) an in-plane single-electron electrometer formed adjacent to the edge of one of the SSTDs, (2) a micro-ESR device formed by using a metallic waveguide and placed near the SOINW interconnect, and (3) a nanomagnet which generates a magnetic field gradient across the single-spin qubits. By integrating all the building-blocks in a nanoscale footprint, we fully investigate initialization, selective manipulation and readout of the single-spin qubits for the first time on Si.

Recently, an influential American business magazine, Forbes, chose Quantum Engineering as one of its top 10 majors (degree programmes) for 2022. According to Forbes magazine (September 2012): "a need is going to arise for specialists capable of taking advantage of quantum mechanical effects in electronics and other products." We propose to renew the CDT in Controlled Quantum Dynamics (CQD) to continue its success in training students to develop quantum technologies in a collaborative manner between experiment and theory and across disciplines. With the ever growing demand for compactness, controllability and accuracy, the size of opto-electronic devices in particular, and electronic devices in general, is approaching the realm where only fully quantum mechanical theory can explain the fluctuations in (and limitations of) these devices. Pushing the frontiers of the 'very small' and 'very fast' looks set to bring about a revolution in our understanding of many fundamental processes in e.g. physics, chemistry and even biology with widespread applications. Although the fundamental basis of quantum theory remains intact, more recent theoretical and experimental developments have led researchers to use the laws of quantum mechanics in new and exciting ways - allowing the manipulation of matter on the atomic scale for hitherto undreamt of applications. This field not only holds the promise of addressing the issue of quantum fluctuations but of turning the quantum behaviour of nano- structures to our advantage. Indeed, the continued development of high-technology is crucial and we are convinced that our proposed CDT can play an important role. When a new field emerges a key challenge in meeting the current and future demands of industry is appropriate training, which is what we propose to achieve in this CDT. The UK plays a leading role in the theory and experimental development of CQD and Imperial College is a centre of excellence within this context. The team involved in the proposed CDT covers a wide range of key activities from theory to experiment. Collectively we have an outstanding track record in research, training of postgraduate students and teaching. The aim of the proposed CDT is to provide a coherent training environment bringing together PhD students from a wide variety of backgrounds and giving them an appreciation of experiment and theory of related fields under the umbrella of CQD. Students graduating from our programme will subsequently find themselves in high-demand both by industry and academia. The proposed CDT addresses the EPSRC strategic area 'Quantum Information Processing and Quantum Optics" and one of the priority areas of the CDT call, "Towards Quantum Technologies". The excellence of our doctoral training has been recognised by the award of a highly competitive EU Innovative Doctoral Programme (IDP) in Frontiers of Quantum Technology, which will start in October 2013 running for four years with the budget around 3.8 million euros. The new CDT will closely work with the IDP to maximise synergy. It is clear that other high-profile activities within the general area of CQD are being undertaken in a range of other UK universities and within Imperial College. A key aim of our DTC is inclusivity. We operate a model whereby academics from outside of Imperial College can act as co-supervisors for PhD students on collaborative projects whereby the student spends part of the PhD at the partner institution whilst remaining closely tied to Imperial College and the student cohort. Many of the CDT activities including lectures and summer schools will be open to other PhD students within the UK. Outreach and transferable skills courses will be emphasised to provide a set of outreach classes and to organise various outreach activities including the CDT in CQD Quantum Show to the general public and CDT Festivals and to participate in Imperial's Science Festivals.