1,440 research outputs found
A new kind of heterodyne measurement of coherent population trapping in an atomic beam
A new heterodyne technique is presented for the simultaneous measurement of dispersion and absorption of atomic transitions useful especially for coherent two photon transitions. This technique is compared with traditional homodyne interferometer and with modern frequency modulation techniques. First results are the properties of a coherent population trapping (CPT) scheme realized in a cesium atomic beam. The measured linewidth of the CPT-resonance is reverse similar, equals 300 kHz (FWHM) with a residual absorption of less than 2 Ă 10â3 cmâ1 and the dispersion is equivalent to a group velocity of vg â c/5000
A bound on Planck-scale modifications of the energy-momentum composition rule from atomic interferometry
High sensitivity measurements in atomic spectroscopy were recently used in
Amelino-Camelia et. al. to constraint the form of possible modifications of the
energy-momentum dispersion relation resulting from Lorentz invariance violation
(LIV). In this letter we show that the same data can be used successfully to
set experimental bounds on deformations of the energy-momentum composition
rule. Such modifications are natural in models of deformed Lorentz symmetry
which are relevant in certain quantum gravity scenarios. We find the bound for
the deformation parameter to be a few orders of magnitude below the
Planck scale and of the same magnitude as the next-to-leading order effect
found in Amelino-Camelia et. al. We briefly discuss how it would be possible to
distinguish between these two scenarios.Comment: 5 pages, some comments and references adde
Optical resonator with steep internal dispersion
We present an optical resonator with modified properties due to a nonabsorbing highly dispersive medium. The steep nonabsorbing dispersion is created with an additional pump field in an atomic beam using the effect of coherent population trapping. The linewidth of such a resonator depends on the slope of the dispersion line, which in turn depends on the atomic density and the intensity of pump and probe field. In the experiments presented here, the cavity linewidth is reduced by a factor of more than 50 relative to the linewidth of the empty resonator. We have studied the influence of the relative intensities of pump and probe field on the line profile. Due to the dispersion of the medium, the resonance frequency is nearly independent of the geometrical length of the resonator
Improved Term of the Electron Anomalous Magnetic Moment
We report a new value of electron , or , from 891 Feynman diagrams
of order . The FORTRAN codes of 373 diagrams containing closed
electron loops have been verified by at least two independent formulations. For
the remaining 518 diagrams, which have no closed lepton loop, verification by a
second formulation is not yet attempted because of the enormous amount of
additional work required. However, these integrals have structures that allow
extensive cross-checking as well as detailed comparison with lower-order
diagrams through the renormalization procedure. No algebraic error has been
uncovered for them. The numerical evaluation of the entire term by
the integration routine VEGAS gives , where the
uncertainty is obtained by careful examination of error estimates by VEGAS.
This leads to ,
where the uncertainties come from the term, the estimated
uncertainty of term, and the inverse fine structure constant,
, measured by atom interferometry combined
with a frequency comb technique, respectively. The inverse fine structure
constant derived from the theory and the Seattle
measurement of is .Comment: 64 pages and 10 figures. Eq.(16) is corrected. Comments are added
after Eq.(40
High-accuracy Penning trap mass measurements with stored and cooled exotic ions
The technique of Penning trap mass spectrometry is briefly reviewed
particularly in view of precision experiments on unstable nuclei, performed at
different facilities worldwide. Selected examples of recent results emphasize
the importance of high-precision mass measurements in various fields of
physics
White-light cavities, atomic phase coherence, and gravitational wave detectors
We propose a new concept to realize optical cavities with large buildup but broadband response (white-light cavities) using atomic phase coherence. We demonstrate that strongly driven double-Î systems can show negative dispersion without absorption, which is needed in order to compensate for the variation of the wavelength with frequency. Internal buildup profiles and the cavity bandwidth of standard devices and white-light cavities will be briefly compared. These devices may be useful to improve the bandwidth and sensitivity of future generations of laser interferometric gravitational wave detectors
Improved Term of the Muon Anomalous Magnetic Moment
We have completed the evaluation of all mass-dependent QED
contributions to the muon , or , in two or more different
formulations. Their numerical values have been greatly improved by an extensive
computer calculation. The new value of the dominant term is 132.6823 (72), which supersedes the old value 127.50 (41).
The new value of the three-mass term
is 0.0376 (1). The term is crudely estimated to
be about 0.005 and may be ignored for now. The total QED contribution to
is , where 0.02 and
1.15 are uncertainties in the and terms and 0.85 is from
the uncertainty in measured by atom interferometry. This raises the
Standard Model prediction by , or about 1/5 of the
measurement uncertainty of . It is within the noise of current
uncertainty () in the estimated hadronic
contributions to .Comment: Appendix A has been rewritten extensively. It includes the 4th-order
calculation for illustration. Version accepted by PR
Probing the quantum-gravity realm with slow atoms
For the study of Planck-scale modifications of the energy-momentum dispersion
relation, which had been previously focused on the implications for
ultrarelativistic (ultrafast) particles, we consider the possible role of
experiments involving nonrelativistic particles, and particularly atoms. We
extend a recent result establishing that measurements of "atom-recoil
frequency" can provide insight that is valuable for some theoretical models.
And from a broader perspective we analyze the complementarity of the
nonrelativistic and the ultrarelativistic regimes in this research area.Comment: LaTex, 13 page
Optical Clocks in Space
The performance of optical clocks has strongly progressed in recent years,
and accuracies and instabilities of 1 part in 10^18 are expected in the near
future. The operation of optical clocks in space provides new scientific and
technological opportunities. In particular, an earth-orbiting satellite
containing an ensemble of optical clocks would allow a precision measurement of
the gravitational redshift, navigation with improved precision, mapping of the
earth's gravitational potential by relativistic geodesy, and comparisons
between ground clocks.Comment: Proc. III International Conference on Particle and Fundamental
Physics in Space (SpacePart06), Beijing 19 - 21 April 2006, to appear in
Nucl. Phys.
Nanoporous films with low refractive index for large-surface broad-band anti-reflection coatings
Nowadays, nanoporous films are widely employed in biochemical applications or in opto-photonic devices such as displays, solar cells, or light-guiding systems. In particular, the technological feasibility of nanoporous layers with low refractive indices has recently enabled the development of high-efficiency anti-reflection coatings. In this paper, we report on hybrid polymer nanoporous films that can be fabricated in a single coating step with an industrial aqueous-based method on very large surfaces. Both high transparency and low refractive index are simultaneously achieved over the entire visible spectrum. We eventually demonstrate the potential of such films for broadband AR applications by combining them in a graded-index multilayer that reduces the surface reflectivity of a polymer substrate from 10% to few â°
- âŠ