We describe our efforts to study the physics of the fractional quantum Hall effect using ultracold quantum gases in an optical lattice and to perform precision measurements using large-area atom interferometry.
Like 64 submit reddit Exclusive excerpt from Nobel Laureate Charles H. Townes's book, How the Laser Happened: Adventures of a Scientist (published by Oxford University Press in 2002). In this book, Townes provides a highly personal look at some of the leading events in twentieth-century physics. Townes was inventor of the maser, of which the laser is one example; an originator of spectroscopy using microwaves; and a pioneer in the study of gas clouds in galaxies and around stars. Throughout his career he has also been deeply engaged with issues outside of academic research. He worked on applied research projects for Bell Labs; served on the board of directors for General Motors; and devoted extensive effort to advising the US government on science, policy, and defense.
We present a test of the local Lorentz invariance of post-Newtonian gravity by monitoring Earth's gravity with a Mach-Zehnder atom interferometer that features a resolution of about 8×10−9 g/ √ Hz, the highest reported thus far. Expressed within the standard model extension (SME) or Nordtvedt's anisotropic universe model, the analysis limits four coefficients describing anisotropic gravity at the ppb level and three others, for the first time, at the 10ppm level. Using the SME we explicitly demonstrate how the experiment actually compares the isotropy of gravity and electromagnetism.PACS numbers: 03.75. Dg, 11.30.Cp, 11.30.Qc, 04.25.Nx The description of gravitation by a dynamic geometry of space-time, Einstein's general relativity (GR), is based on the Einstein equivalence principle. This encompasses the universality of free fall (UFF), local position invariance (LPI), and local Lorentz invariance (LLI), which also underlies the non-gravitational standard model of particle physics. Attempts to unify GR and the standard model have failed so far. This suggests that one of their foundations might be violated at some level of precision [1]. So far, tests of the UFF and LPI have not identified violations [1]. LLI has been tested experimentally for many sectors of the standard model, such as for photons ('Maxwell sector'), electrons, protons, and neutrons [1,2,3]. No Lorentz violation has been identified, although the coverage of parameter space is still incomplete. Far less attention, however, has been paid to the LLI of the gravitational ('Einstein') sector, in spite of the pioneering work of Nordtvedt and Will in the 1970ies. Motivated by that fact that anisotropies arise in various theories of gravity other than GR [4], they have ruled out a Lorentz-violating anisotropy in gravity by searching for an anomalous time-dependence of the acceleration of free fall g on Earth [4,5,6].The success of GR and the standard model implies that any Lorentz violations are tiny. This and the relative weakness of gravity means that only exceptionally sensitive experiments can hope to detect Lorentz violation in gravity. A relatively recent addition to these is precision atom interferometry [7,8]. This has been serving, for example, in measurements of the fine structure constant [9], g [10] and its gradient [11], the Sagnac effect [12], and Newton's constant G [13] with sensitivities that compare favorably with other state-of-the-art instruments. One reason for its outstanding precision is that the motion of neutral atoms can realize a freely falling frame to a * Electronic address: holgerm@stanford.edu high accuracy and that this motion can be interrogated by laser radiation in a tremendously precise way. As a result, tests of post-Newtonian gravity with atom interferometry have been proposed that could rival or exceed the precision of classical ones [14].Here, we report on a first step in this direction: We describe the highest resolution atomic gravimeter reported thus far [15]. We then analyze the influence of Lorentz violat...
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