Bulletin of the American Physical Society
42nd Annual Meeting of the APS Division of Atomic, Molecular and Optical Physics
Volume 56, Number 5
Monday–Friday, June 13–17, 2011; Atlanta, Georgia
Session J2: Fundamental Symmetry Tests |
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Chair: David DeMille, Yale University Room: A602 |
Wednesday, June 15, 2011 10:30AM - 11:00AM |
J2.00001: Interferometry with Bose Einstein condensates in extended free fall Invited Speaker: This talk will give a status report about interferometry with extended wave packets at nanoKelvin energy scales. Motivation is performing tests of gravity with quantum objects. The experiments use a chip-based atom laser. [Preview Abstract] |
Wednesday, June 15, 2011 11:00AM - 11:30AM |
J2.00002: The size of the proton Invited Speaker: A measurement of the Lamb shift (2S--2P energy difference) in muonic hydrogen ($\mu$p, the exotic hydrogen atom made from a proton and a negative muon $\mu^-$) has been on the physicists' wish list for more than 40 years. Due to its 200 times larger mass, the muon's Bohr radius in $\mu$p is only 1/200 of the electron's Bohr radius in regular hydrogen (H). This enhances finite size effects by about $200^3$ in $\mu$p, compared to H. The proton's finite size $r_p$ affects the 2S Lamb shift in $\mu$p by as much as 2\%, making $\mu$p a unique, clean, atomic system to study $r_p$ using laser spectroscopy. We have recently observed the first transitions in muonic hydrogen~[1] and muonic deuterium~[2]. The $2S_{1/2}^{F=1}$ to $2P_{3/2}^{F=2}$ transition in $\mu$p was found at 49881.88(76)\,GHz [1]. Even with this - by laser spectroscopy standards - very moderate accuracy of 760\,MHz (4\% of the natural line width) we can deduce $r_p$ 10 times more accurately than the CODATA world average [3]. We obtain $r_p\,=\,0.84184(67)$\,fm~[1]. The accuracy of $r_p$ is limited by the uncertainty of the proton polarizability which is enters the theory relating the measured frequency to $r_p$. We have also measured a second transition in $\mu$p ( $2S_{1/2}^{F=0}$ to $2P_{3/2}^{F=1}$ ) [2]. It confirms our value~[1] of $r_p$, and provides the first determination of the 2S hyperfine splitting (HFS) in $\mu$p. The HFS reveals the Zemach radius, i.e. the radius of the magnetization distribution inside the proton. Now there is a ``proton size puzzle.'' We found the resonance~[1] 75\,GHz (i.e. 4 natural line widths) away from the expected position. Our $r_p$ is 10 times more accurate, but 4\% ($5 \sigma$) smaller than the CODATA value~[3]. There are still surprises in physics.\\[4pt] [1] R. Pohl et al. (CREMA collaboration), Nature 466, 213 (July 2010).\\[0pt] [2] CREMA collaboration, to be published.\\[0pt] [3] P.J.~Mohr, B.N.~Taylor and D.B.~Newell, Rev.~Mod.~Phys. 80, 633 (2008). [Preview Abstract] |
Wednesday, June 15, 2011 11:30AM - 12:00PM |
J2.00003: Concepts for an optical nuclear clock with Th-229 Invited Speaker: The transition between the nuclear ground state and the low-lying isomeric state in Th-229 at about 160 nm wavelength will allow to apply methods of high-resolution laser spectroscopy to a nuclear excitation, opening a new field at the border between atomic and nuclear physics. It also offers the potential for a highly precise optical clock using this transition frequency as a reference. I will describe these concepts and, more specifically, our experiment towards a two-photon excitation of the nuclear transition in Th$^+$ ions, using electron bridge processes within the dense electronic level structure of this ion. [Preview Abstract] |
Wednesday, June 15, 2011 12:00PM - 12:30PM |
J2.00004: Al$^{+}$ optical clocks for fundamental physics, geodesy, and quantum metrology Invited Speaker: Laser-cooled trapped atoms have long been recognized as potentially very accurate frequency standards for clocks. Ultimate accuracies of 10$^{-18}$ to 10$^{-19}$ appear possible, limited by the time-dilation of trapped ions that move at laser-cooled 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$^{+}$ ``quantum-logic'' clocks, the current accuracy of 8.6$\times $10$^{-18}$ has enabled a geo-potential-difference measurement that detected a height change of 37$\pm $17 cm due to the gravitational red-shift. We have also observed quantum coherence between two Al$^{+}$ ions with a record Q-factor of 3.4$\times $10$^{16}$, and compared the Al$^{+}$ resonance frequency to that of a single Hg$^{+}$ ion to place limits on the temporal variation of the fine-structure constant. This work is done in collaboration with D. B. Hume, M. J. Thorpe, D. J. Wineland, and T. Rosenband. [Preview Abstract] |
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