New applications of dark states in metrology and quantum control -- Visiting Researcher

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When an atomic system is prepared in a coherent superposition state, extremely narrow Coherent Population Trapping (CPT) and related Electromagnetically Induced Transparency (EIT) resonances can be observed where the atomic coherence cancels, or reduces, absorption.The relevant early studies include measurements performed in Pisa where terms such as dark resonance and atomic population trapping were introduced. The recently expanding interest in the topic is due not only to the fascinating physics involving quantum coherence but also to the fact that there are many potential applications with relevance both in development of new techniques and devices, and in new approaches to fundamental studies, such as slowing oflight, nonlinear optics, quantum information storage, frequency standards, and precisemagnetometers. In the context of frequency standards, it should be noticed that CPT based atomic clocks have been studied in detail by the NIST group, and the first commerciallyavailable Coherent Population Trapping atomic frequency standard is now produced by Kernco, Inc (www.kernco.com).The research described here aims to investigate experimentally new applications of dark states in the domain of metrology and quantum control. This will be done by using cold atoms confined in a dipole trap. This offers significant advantages with respect to a thermal atomic vapour, as commonly used in EIT/CPT studies, and it is essential for the investigation envisaged here. Both measurement on a large cloud of atoms, and on a single trapped atom are planned.The proposer has already made a significant amount of background work needed for the proposed research. A collaboration was also started with Prof. Brana Jelenkovic (Belgrade, Serbia) to acquire the necessary expertise in the techniques specific to the detection and control ofa single atom. Funds are now requested to allow Prof. Jelenkovic to visit UCL for two months during which some key aspects of the experiment will be finalised.