Cavity QED with Diamond Nanocrystals and Silica Microspheres.pdf

Cavity QED with Diamond Nanocrystals and Silica Microspheres Young-Shin Park, Andrew K. Cook, and Hailin Wang* Department of Physics, University of Oregon, Eugene, Oregon 97403, USA *Corresponding author. Tel: 1-541-346-4758. Fax: 1-541-346-4315. E-mail: hailin@uoregon.edu Abstract Normal mode splitting is observed in a cavity QED system, in which nitrogen vacancy centers in diamond nanocrystals are coupled to whispering gallery modes in a silica microsphere. The composite nanocrystal-microsphere system takes advantage of the exceptional spin properties of nitrogen vacancy centers as well as the ultra high quality factor of silica microspheres. The observation of the normal mode splitting indicates that the dipole optical interaction between the relevant nitrogen vacancy center and whispering gallery mode has reached the strong coupling regime of cavity QED. Interactions of single atoms with electromagnetic fields in a microresonator have been a central paradigm for the understanding, manipulation, and control of quantum coherence and entanglement [1- 4]. Of particular importance is the regime of strong coupling, characterized by a reversible exchange of excitation between an atom and cavity fields. This coherent exchange can induce atom-photon, atom- atom, and photon-photon entanglement and plays a key role in many quantum information processes. Strong-coupling cavity QED has been realized with trapped atoms and with solid-state systems using quantum dots and Cooper pair boxes as artificial atoms [5-9]. A solid-state cavity QED system circumvents the complexity of trapping single atoms in a microresonator and can potentially enable scalable device fabrications. 1 In order to use the strong-coupling process for quantum control of entanglement in a solid-state environment, the cavity QED system needs to feature a robust spin coherence, since coupling to the surrounding environment leads to rapid decay of most other forms of quantum