Semiconductor Quantum Photonics: Control of Spin, Exciton and Photon Interactions by Nano-Photonic Design

We seek to exploit the highly advantageous properties of III-V semiconductors to achieve agenda setting advances in the quantum science and technology of solid state materials. We work in the regime of next generation quantum effects such as superposition and entanglement, where III-V systems have many favourable attributes, including strong interaction with light, picosecond control times, and microsecond coherence times before the electron wavefunction is disturbed by the environment.
We employ the principles of nano-photonic design to access new regimes of physics and potential long term applications. Many of these opportunities have only opened up in the last few years, due to conceptual and fabrication advances. The conceptual advances include the realisation that quantum emitters emit only in one direction if precisely positioned in an optical field, that wavepackets which propagate without scattering may be achieved by specific design of lattices, and that non-linearities are achievable at the level of one photon and that quantum blockade can be realised where one particle blocks the passage of a second.
The time is now right to exploit these conceptual advances. We combine this with fabrication advances which allow for example reconfigurable devices to be realised, with on-chip control of electronic and photonic properties. We take advantage of the highly developed III-V fabrication technology, which underpins most present day solid-state light emitters, to achieve a variety of chip-based quantum physics and device demonstrations.
Our headline goals include reconfigurable devices at the single photon level, a single photon logic gate based on the fully confined states in quantum dots positioned precisely in nano-photonic structures, and coupling of states by designed optical fields, taking advantage of the reconfigurable capability, to enhance or suppress optical processes. Quantum dots also have favourable spin (magnetic moments associated with electrons) properties. We plan to achieve spins connected together by photons in an on-chip geometry, a route towards a quantum network, and long term quantum computer applications. As well as quantum dots, III-V quantum wells interact strongly with light to form new particles termed polaritons. We propose to open the new field of topological polaritonics, where the nano-photonic design of lattices leads to states which are protected from scattering and where artificial magnetic fields are generated. This opens the way to new coupled states of matter which mimic the quantised Hall effects, but in a system with fundamentally different wavefunctions from electrons.
Finally our programme also depends on excellent crystal growth. We target one of the main issues limiting long term scale up of quantum dot technologies, namely site control. We will employ two approaches, which involve a combination of patterning, cleaning and crystal growth to define precisely the quantum dot location, both based around the formation of pits to seed growth in predetermined locations. Success here will be a major step in bringing semiconductor quantum optics into line with the position enjoyed by the majority of established semiconductor technologies where scalable lithographic processes have been a defining feature of their impact.

We will achieve impact in three directions: Industrial Engagement, Policy Maker and Public Engagement, and Training.

Industrial engagement: The links with our industrial project partners provide immediate routes. Toshiba are the principal company engaged in Quantum Science and Technology research in the UK. We already have an InnovateUK grant with them. In the new grant Toshiba will be active participants with direct involvement, leading to very profitable industrial engagement. The Toshiba interactions also provide a clear exploitation route, most directly for the site-deterministic quantum dot growth work. We also have close involvement with Hitachi, with a high level of scientific collaboration over the last four years (6 joint publications); this will continue strongly in a new grant. We will have active engagement with the Quantum Technology Hubs at York and Oxford. Participation in their Open Days and User Forums will provide excellent opportunities to build links to their wide networks of industry supporters, as proposed in letters from their Directors. One day visits will be made to companies to inform them of our outputs. We have several working models on quantum science and its applications. These will be taken to the companies to show during the visit, and offered on loan for periods of one to two weeks. In addition, two one day conferences will be organised to which industrial personnel will be invited, further promoting Impact.

Policy maker and public engagement: In the last 2-3 years our activities have had many aspects which we will continue strongly in a new grant. We have produced three widely viewed YouTube videos (>35000 hits). The videos were a major factor in our being chosen for an exhibit at the Royal Society Summer Exhibition (RSSE) in 2015, attended by >15000 people. As part of the RSSE we prepared four hands-on demonstrations on Quantum Light, a significant resource for future outreach. The participation at the RSSE and the existence of the demonstrations were significant factors in our being chosen to make a presentation to the Science Minister Jo Johnson in July 2015. We have also given a BBC-radio interview on quantum physics, have met with local MPs and MEPs and given secondary school outreach talks. Such activities will be strongly pursued in a new grant. These include presentation at other science festivals using some of the existing demonstrations but refreshed to include new ones, to prepare additional YouTube videos, and to apply for a RSSE presentation in 2018/19. We will build on our contacts with a BBC producer to achieve further BBC interviews, and will target meetings with additional MPs, beyond those we have met with in the last 3 years (local MPs, MEPs).

Training of highly qualified personnel: We will train 8 postdoctoral workers and 15 PhD students to high levels in physics, optics, fabrication and crystal growth, during the course of the grant. All these topic areas are highly relevant industrially and academically. The researchers will receive considerable training in oral presentation skills, both internally, and externally at international conferences. This will be accompanied by much practice in writing up results for publication. The training in professional skills will be supplemented by encouraging attendance at university-run courses in written and presentational skills and CV preparation. The combination of participation in research at a high level, together with the oral, written and organisational skills described above, will prepare outgoing members very well for future careers in industry and academia. In the last 10 years, 40 former members of the Sheffield group have taken up positions in industry and academia (~50/50 split), including 5 at Oclaro, 3 at Toshiba, and 1 each at Hitachi, Intel, Huawei, Sagentia, Attocube, AMRC, EDF, Phase Focus and NPL showing the range of skill-sets we transfer to our researchers to be much in demand.