Micro cavities for efficient atom-photon coupling by quantum-electrodynamic effects (project supervised by A. Kuhn, Oxford, including secondments

High-finesse optical cavities, which use strongly curved mirrors to confine light to a small volume, have made it possible to efficiently extract a single photon from a single atom, ion, or other quantum emitter. Current state-of-the-art cavities with radii of curvature (ROC) of 5cm ROC have reached the beginning of the strong-coupling regime, where the interaction in the cavity is comparable to rate of uncontrolled spontaneous emission. Such cavities achieve ~50% photon extraction efficiency and allow for controlling the polarisation and temporal profile of the photon.
The aim of this project is to explore, design and construct new microscopic cavities with a 1mm ROC. The tighter confinement would lead to an unprecedented 10x improvement in coupling strength, which would allow the exploration of Quantum Electro-dynamical phenomena deep within the strong-coupling regime, as well as allowing more efficient photon extraction. Beside the characterisation, testing and assembly of novel cavities, the project is equally aiming at the in-situ demonstration of their capabilities in connection with single atoms trapped in the mode volume of the cavity field.
The project pushes the field of cavity quantum electrodynamics into the ultra-strong coupling regime, and will need the student to co-ordinate the production of cavities between several research groups. There would be opportunities to travel to Sussex to use the mirror machining apparatus and to mirror-coating companies in the US and in Germany.
The research team of Dr Kuhn does encompass two PostDocs and four graduate students which operate 2-4 laboratories dedicated to cavity-qed and atom-photon coupling in cavities at Physics department of the University of Oxford. The work space is well equipped, comprising 3-4 vacuum chambers for studying atom-photon coupling in cavities, several ECDL and fibre lasers for atom manipulation, a frequency comb for synchronously stabilising all laser and cavity frequencies, a large battery of single-photon counters and a cavity-characterisation setup and an AFM for the close inspection of mirror surfaces. Furthermore access to the CO2-laser machining facility in Sussex and the Ion-Beam-Milling apparatus at Oxford materials will be integral part of this project.
This project will impact upon the NQIT Hub, one of the UKNQTP's Quantum Technologies Hubs within EPSRC's Quantum Technologies research area. It will contribute to NQIT's milestones, most significantly to achieve a highly-curved mirror surface, using focussed ion beam milling and laser machining in collaboration with NQIT partners Smith and Keller. Furthermore, the specification and production of high-finesse mirror coatings would require a close collaboration with mirror-coating companies such as LaserOptik in Garbsen or ATF in Boulder. The project would accelerate achievement of the milestones M2.3 High-finesse fibre cavity, M2.4 Atom-cavity coupling, M2.5 Strong cavity coupling, M2.7 Cavity-mediated remote entanglement. All necessary apparatus exists within NQIT, including ion-beam milling (Oxford Materials), CO2 laser machining system (Sussex), wavefront sensor and AFM for characterising the mirror surfaces (Oxford Physics), and all necessary lasers for driving the photon production process (Oxford Physics).