Session G2: Invited Session: Precision Measurements

Advancing the state-of-the-art of the optical atomic clock

The continued advance in laser phase coherence has permitted an improvement of the stability of optical lattice clocks by a factor of 10. This measurement precision has facilitated characterization of systematic effects, allowing us to improve the lattice clock accuracy by a factor of 20. The accuracy and stability of the JILA Sr clock now reach the 10$^{-18}$ level. Owing to these advances, the lattice clock has also emerged as an effective laboratory to study many-body spin correlations.   

Fundamental tests of nature and a precision measurement of the electron mass

The presentation will provide an overview on recent fundamental applications of precision measurements with cooled and stored ions in Penning traps. One the one hand, precision Penning-trap mass measurements provide indispensable information for neutrino physics and for testing fundamental symmetries. On the other hand, in-trap measurements of the bound-electron $g$-factor in highly-charged hydrogen-like ions allow for better determination of fundamental constants and for constraining Quantum Electrodynamics. Furthermore, ongoing preparations for the experimental comparison of the proton and antiproton g-factors will allow us to achieve a crucial test of the Charge-Parity-Time reversal symmetry. Among others a substantial improvement of the atomic mass of the electron by combining a very accurate measurement of the magnetic moment of a single electron bound to a carbon nucleus with a state-of-the-art calculation in the framework of bound-state Quantum Electrodynamics will be presented. The achieved precision of the atomic mass of the electron surpasses the current CODATA value by a factor of 13.   

Atom Interferometric Measurements of Atomic Structure

Measurements of atomic polarizability, tune-out wavelengths, and van der Waals potentials made with an atom interferometer all serve as benchmark tests for atomic structure calculations. We used a Pritchard-type atom interferometer with phase shifts caused by electric field gradients in order to measure electric polarizabilities of Na, K, and Rb atoms [1]. We reported ratios of static polarizabilities $\alpha_{Rb}$/$\alpha _{Na}=$1.959(5) with 0.3 percent uncertainty. We studied atomic phase shifts due to laser light in order to measure a tune-out wavelength (where there is a root in dynamic polarizability) for potassium atoms of $\lambda _{zero}=$768.9712 nm with 1.5 pm uncertainty [2]. Finally, we measured atom-surface interactions with 2 percent precision, which was sufficient to detect the impact of Rb atomic core electrons on van der Waals potentials [3]. These serve as independent benchmarks for atomic structure calculations because polarizability depends on sums of oscillator strengths, tune-out wavelengths depend on ratios of oscillator strengths, and atom-surface van der Waals interactions depend on sums of oscillator strengths weighted by resonance frequencies. Advances in the atom interferometry measurement techniques used for these and next generation measurements will be discussed. \\[4pt] [1] Phys Rev A 81, 053607 (2010)\\[0pt] [2] Phys. Rev. Lett. 109, 243004 (2012)\\[0pt] [3] Phys. Rev. Lett. 105, 233202 (2010)   

Precision Inertial Sensing Using Atom Interferometry

Recent advances in atom optics and atom interferometry have enabled observation of atomic de Broglie wave interference when atomic wavepackets are separated by distances approaching 10 cm and times of nearly 3 seconds. With further refinements, these methods may lead to meter- scale superpositions. In addition to providing new tests of quantum mechanics, these methods allow inertial force sensors of unprecedented sensitivity. We will describe methods demonstrated and results obtained in a 10 m atomic fountain configuration [1-2], their implications for technological applications in geodesy and inertial navigation, and their relevance to fundamental studies in gravitational physics [3]. We will describe supporting techniques used to cool atoms to effective temperatures of $\sim$ 15 pK in two dimensions and novel atom optics configurations which have achieved greater than 5 sec of quasi-inertial free fall. Finally, we will discuss the prospects of incorporating spin-squeezing methods to improve interferometer signal-to-noise. \\[4pt] [1] Dickerson, Susannah M., Jason M. Hogan, Alex Sugarbaker, David M. S. Johnson, and Mark A. Kasevich. ``Multiaxis Inertial Sensing with Long-Time Point Source Atom Interferometry.'' Physical Review Letters 111, no. 8 (August 19, 2013): 083001.\\[0pt] [2] Sugarbaker, Alex, Susannah M. Dickerson, Jason M. Hogan, David M. S. Johnson, and Mark A. Kasevich. ``Enhanced Atom Interferometer Readout through the Application of Phase Shear.'' Physical Review Letters 111, no. 11 (September 10, 2013): 113002.\\[0pt] [3] Graham, Peter W., Jason M. Hogan, Mark A. Kasevich, and Surjeet Rajendran. ``New Method for Gravitational Wave Detection with Atomic Sensors.'' Physical Review Letters 110, no. 17 (April 25, 2013): 171102.