Planned research - New materials for coherently prepared media

Positions to be opened: 1 PhD student, 1 MSc student

Over the years many groups have shown a significant increase in interest in new materials for CPM. The most promising media studied so far have been quantum dots, various ions in crystal matrices, gas-filled hollow optical fibers, and diamond crystals with nitrogen-vacancy (NV) color centers. Within the TEAM project research on gas-filled hollow optical fibers and diamond crystals with NV color centers is planned.

Photonic crystal fibers (PCF) are a new type of optical fibers which transmit light based on different physical mechanism and hence possessing other optical propert than traditional fibers. One of the interesting features of PCF is existence of air channels which can be filled with different material (gas or liquids). Introduction of these meterials enables analysis of the light-atom interaction under new physical conditions.

Two types of PCFs are forseen for studies of CPM: hollow-core and suspended-core photonic crystal fibers. These fibers filled with suitable atomic or molecular gases can, to some extend, replace vapor cells in experiments where gas media are used. For instance, similar techniques, as applied for the above described task of quantum-state engineering, can be used for creation and detection of quantum superposition, hence for preparation of CPM. The advantage offered by hollow fibers over other techniques is that the different mechanism of light propagation providing extra degrees of freedom for tailoring CPM for specific applications. A serious problem which will need to be addressed is the protection against relaxation/decoherence on the internal fiber-channel walls. This will require special coating technology which remains to be developed. One PhD student accompanied by a MSc student are foreseen for this research. They will prepare the experimental setup and master ways of atom filling and wall coating. Next steps will be observation of the specific signatures of CPM, such as electromagnetically-induced transparency and/or nonlinear magneto-optical rotation and optimization of the setup performance. During the preparation stage, the MSc student task will be to focus on numerical simulation of the desired hollow fiber structures.

Another approach which we want to pursue in context of new materials for CPM are the NV colour centers in diamond crystals. Such centers have strong and narrow absorption and emission lines in the visible and most importantly possess an electron spin, and hence exhibit magnetism. They can be regarded as paramagnetic "artificial atoms" with the properties which can be controlled by external fields. It implies a possibility of their usage as miniature sensors. Moreover, their ground-state structure allows reaching very long relaxation times so they are good candidates for quantum-state engineering with the use of techniques similar to those developed for atoms. So far such samples have been exclusively studied by detecting fluorescence light emitted by single centers. Our idea worked out with the Berkeley partners is to apply the transmission methodology and to work with bulk diamond crystals. In this study we are mainly interested in finding which parameters of the samples are critical for their best magnetometric performance and longest lifetimes and how to implement the techniques developed for atomic CPM to NV-diamond samples. Moreover, we want to work with other, less known crystal samples which are likely to exhibit properties similar to the NV diamonds.

This task will require involvement of one PhD student (position possibly split into two shorter term periods each dedicated to a particular medium) and one MSc student.

We will cooperate on this subject with D. Budker's (Berkeley) and G. Djotyan's (Budapest) groups.