冷却イオンセミナー

======= 新学術領域「実験と観測で解き明かす中性子星の核物質」セミナー =========

           クーロン結晶光学時計と対称性の自発的破れ(Kibble-Zurek機構)の検証

日時:2月21日(金)14:30~16:00
場所:東北大学 理学総合研究棟721号室

講師:Dr. Tanja E. Mehlstaubler (PTB, ドイツ連邦物理技術研究所 冷却イオン量子センサーチームリーダー)

題目:Optical Clocks with Coulomb Crystals and Fundamental Physics 

要旨:

Our work focuses on the realization of an optical ion clock with a fractional frequency inaccuracy as low as 10-18 and improved short-term stability. It is based on multiple 115In+ ions which are sympathetically cooled by 172Yb+ ions.

Within an European joint research project we develop chip-based linear ion traps for quantum metrology. In our prototype trap [1,2] we characterized excess micromotion and demonstrated sympathetic cooling of In+/Yb+-crystals. We showed that our trap design provides a highly controllable environment for precision spectroscopy and experiments with ion Coulomb crystals [2]. An advanced next generation ion trap, will be based on gold coated aluminum nitride wafers, which are laser machined at LZH and PTB.

 

In the second part of my talk, I will discuss the formation of ion Coulomb crystals in such ion traps with low micromotion.

 

Structural defects in ion Coulomb crystals (kinks) have been proposed for studies of quantum-mechanical effects with solitons and as carriers of quantum information [3]. Defects form when a symmetry breaking phase transition is crossed and the finite speed of information prevents different regions from coordinating the choice of the symmetry broken state. Where such local choices are incompatible, defects will form with densities predicted to follow a power law scaling in the rate of the transition. The importance of this Kibble-Zurek mechanism (KZM) ranges from cosmology to condensed matter [4]. In previous tests in homogeneous systems, defect formation was seen, but weak dependence on the transition rate and limited control of external parameters so far prevented tests of KZM scaling. As recently predicted [5], in inhomogeneous systems propagation of the critical front enhances the role of causality and steepens scaling of defect density with the transition rate. We use ion Coulomb crystals in a harmonic trap to demonstrate, for the first time, scaling of the number of topological defects with the transition rate – the central prediction of KZM - in a well-controlled environment [6]. We will detail on kink dynamics [7] and stability in our system. Implementing mass defects and electric fields we demonstrate first steps to a controlled kink preparation and manipulation for future studies of nonlinear physics in ion Coulomb crystals.

 


[1] Herschbach et al., Appl. Phys. B 107, 891 (2012)

[2] Pyka et al., Appl. Phys. B (2013), DOI: 10.1007/s00340-013-5580-5

[3] Landa et al., Phys. Rev. Lett. 104, 043004 (2010)
[4] Kibble, T.W.B., Phys. Rep. 67, 183 (1980);  Zurek, W. H., Nature 317, 505 (1985)
[5] del Campo et al., Phys. Rev. Lett. 105, 075701 (2010)
[6] Pyka et al., Nat. Commun. 4, 2291 (2013)

[7] Partner et al., New J. Phys. (2013)



連絡先:小池 武志(6451)

∞∞∞∞∞∞∞∞∞∞∞∞∞∞∞∞∞∞∞∞∞∞∞∞∞∞∞∞∞∞∞∞∞∞∞∞∞∞

世話人: 田村 裕和(6455)  酒見 泰寛(7795)  小池 武志(6451)