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

高精细光学腔，使用强烈弯曲的镜子将光限制在一个小体积内，使得从单个原子、离子或其他量子发射体中有效地提取单个光子成为可能。目前最先进的腔体的曲率半径（ROC）为5厘米ROC已经达到了强耦合制度的开始，在腔中的相互作用是不受控制的自发辐射的速率相媲美。这样的腔实现~50%的光子提取效率，并且允许控制光子的偏振和时间分布。该项目的目的是探索，设计和构建具有1 mm ROC的新的显微腔。更严格的限制将导致耦合强度前所未有的10倍提高，这将允许在强耦合机制内深入探索量子电动力学现象，并允许更有效的光子提取。除了表征、测试和组装新型腔体外，该项目还旨在现场演示它们与被困在腔场模体积中的单原子的能力。该项目将腔量子电动力学领域推向超强耦合领域，并需要学生协调多个研究小组之间的腔体生产。将有机会前往苏塞克斯使用镜子加工设备和镜子涂层公司在美国和德国。Kuhn博士的研究团队包括两名博士后和四名研究生，他们在牛津大学物理系经营2-4个实验室，致力于腔QED和腔中的原子光子耦合。工作空间设备齐全，包括3-4个用于研究腔中原子-光子耦合的真空室，几个用于原子操作的ECDL和光纤激光器，一个用于同步稳定所有激光和腔频率的频率梳，一个大型单光子计数器电池和一个腔表征装置以及一个用于密切检查镜面的AFM。此外，进入苏塞克斯的CO2激光加工设施和牛津材料的离子束铣削设备将是该项目的一个组成部分。该项目将影响NQIT中心，该中心是EPSRC量子技术研究领域内的UKNQTP量子技术中心之一。它将有助于NQIT的里程碑，最重要的是实现高弯曲的镜面，使用聚焦离子束铣削和激光加工与NQIT合作伙伴史密斯和凯勒合作。此外，高精细镜面涂层的规格和生产需要与加布森的LaserOptik或博尔德的ATF等镜面涂层公司密切合作。该项目将加速实现里程碑M2.3高精细度光纤腔，M2.4原子-腔耦合，M2.5强腔耦合，M2.7腔介导的远程纠缠。所有必要的设备都存在于NQIT内，包括离子束铣削（牛津材料），CO2激光加工系统（Sussex），波前传感器和AFM用于表征镜面（牛津物理），以及所有必要的激光器用于驱动光子生产过程（牛津物理）。

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).