Details of Grant 

EPSRC Reference:	EP/J002194/1
Title:	Few-Photon Nonlinear Optics in Ultracold Rydberg Gases
Principal Investigator:	Hofferberth, Dr S
Other Investigators:
Researcher Co-Investigators:
Project Partners:
Department:	Sch of Physics & Astronomy
Organisation:	University of Nottingham
Scheme:	Career Acceleration Fellowship
Starts:	01 October 2011	Ends:	30 September 2016	Value (£):	1,142,329
EPSRC Research Topic Classifications:	Cold Atomic Species Light-Matter Interactions Optical Phenomena
EPSRC Industrial Sector Classifications:	No relevance to Underpinning Sectors
Related Grants:
Panel History:	Panel Date Panel Name Outcome 14 Jun 2011 Fellowships 2011 Interview Panel B Announced
Summary on Grant Application Form
Photons are the ideal carriers of information, as is evidenced by the enormous success of optical telecommunication. Improvements in fibre and detection technology allow for ever more efficient and faster information transfer. Ultimately, single photons will be the carriers of such information, in which case the quantum nature of light becomes relevant. At this point, our understanding of information processing has to be completely rewritten, because the often counter-intuitive aspects of quantum mechanics allow for a wholly new approach to information transport and processing. This new field of quantum computing has explosively grown over recent years and tremendous progress is being made. Two major building blocks required in particular for optical quantum computing remain elusive, though. On the one hand, a reliable on-demand source of single optical photons is required to create the photons carrying quantum information exactly when one wants them. Secondly, a robust way to make two photons "see" each other has to be found. Naturally, photons do not interact with each other and only weakly with their environment. But to realize the building blocks of a quantum computer, so-called quantum gates, with single photons, a way has to be found to make photons interact. Both these topics, single-photon source and photon-photon interaction, is the basis of a wide range of research spanning many different areas of modern physics. Although the systems being explored vary greatly in practical implementation, the underlying idea in virtually all cases is to realize optical nonlinearities by creating strong interaction between photons and matter. This can be individual atoms or ions or macroscopic systems such as quantum dots, the goal of current research is to increase these atom-light interactions. In this fellowship programme, I will explore a novel approach, which makes use of strong, but controlled, atom-atom interactions. Using quantum optics control techniques, such as electromagnetically induced transparency, photons can be coherently mapped into atomic excitations. By choosing a high-lying Rydberg state as such an excitation, strong interaction between atoms can be realized as soon as more than one photon is stored. These interactions in turn will alter the photonic quantum state that will later be read out of the medium again. By adding this additional step a strong increase in achievable photon-photon interaction is possible, up to the point of realizing optical nonlinearities on the single photon level, making the above mentioned single-photon source and single-photon quantum gate possible. In the course of this fellowship, this novel idea will be implemented experimentally by combining ultra-cold atom trapping techniques with state-of-the-art photonic crystal fabrication technology. The objective is to create a small-scale integrated system allowing for the manipulation of light on the single photon level inside an optical waveguide. Such a system can form the basic building block of large scale quantum computation and communication networks of the future.
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Organisation Website:	http://www.nottingham.ac.uk