Title: Al+ optical clocks for fundamental physics and geodesy
Speaker: James Chin-wen Chou National Institute of Standards and Technology, Boulder, Colorado, USA
Time: 2011-05-24 14:00-2011-05-24 15:00
Venue: FIT 1-222
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Lasercooled trapped atoms have long been recognized as potentially very accurate frequency standards for clocks. Ultimate accuracies of 1018 to 1019 appear possible, limited by the timedilation of trapped ions that move at lasercooled velocities. The Al+ ion is an attractive candidate for high accuracy, owing to its narrow electronic transition in the optical regime and low sensitivity to ambient field perturbations. Precision spectroscopy on Al+ is enabled by quantum information techniques. With Al+ “quantumlogic” clocks, the current accuracy of 8.6 ×1018 has enabled a geopotentialdifference measurement that detected a height change of 37±17 cm due to the gravitational redshift. We have also observed quantum coherence between two Al+ ions with a record Qfactor of 3.4×1016, and compared the Al+ resonance frequency to that of a single Hg+ ion to place limits on the temporal variation of the finestructure constant. This work is done in collaboration with D. B. Hume, M. J. Thorpe, D. J. Wineland, and T. Rosenband.



Short Bio:

Dr. Chinwen Chou got his bachelor and master degrees in physics at National Taiwan University in Taiwan. In 2000, he joined Prof. Jeff Kimble’s quantum optics group at Caltech. After working on continuousvariable quantum teleportation for two years, Dr. Chou diverted his effort to implementing the DuanLukinCiracZoller (DLCZ) protocol of quantum communication with ensembles of cesium atoms and demonstrated entanglement between remote matter systems for the first time. After getting his Ph.D. in 2006, he did six months of postdoctoral research with Prof. Kimble and demonstrated the first functional quantum nodes in the DLCZ protocol. He then joined the Ion Storage group of Dr. David Wineland in National Institute of Standards and Technology (NIST) at Boulder, Colorado. Since 2007, Dr. Chou has been working on aluminum ion (Al+) optical clocks that exploit quantum logic techniques to enable precision spectroscopy of Al+. The Al+ optical clock he constructed is currently the most accurate clock in the world.