Some possibilities for laboratory searches for variations of fundamental constants

Karshenboim, Savely G.

doi:10.1139/cjp-78-7-639

Cited by 46 publications

(16 citation statements)

References 39 publications

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“…The sensitivity to m s /Λ QCD is relatively weak compared to the 3 other constants. The sensitivity coefficients have now been calculated for a large number of atomic species used in atomic clocks [28,35,37,38,39,40,41,36,42]. Reliable knowledge of these sensitivity coefficient at the 1% to 10% level is required to deduce limits to a possible variation of each of these fundamental parameters by combining the results of several complementary clock comparisons.…”

Section: Einstein Equivalence Principle and Stability Of Fundamental mentioning

confidence: 99%

Cold atom clocks and applications

Bize

Laurent

Abgrall

et al. 2005

J. Phys. B: At. Mol. Opt. Phys.

226

161

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This paper describes advances in microwave frequency standards using laser-cooled atoms at BNM-SYRTE. First, recent improvements of the 133 Cs and 87 Rb atomic fountains are described. Thanks to the routine use of a cryogenic sapphire oscillator as an ultra-stable local frequency reference, a fountain frequency instability of 1.6 × 10 −14 τ −1/2 where τ is the measurement time in seconds is measured. The second advance is a powerful method to control the frequency shift due to cold collisions. These two advances lead to a frequency stability of 2 × 10 −16 at 50 000 s for the first time for primary standards. In addition, these clocks realize the SI second with an accuracy of 7 × 10 −16 , one order of magnitude below that of uncooled devices. In a second part, we describe tests of possible variations of fundamental constants using 87 Rb and 133 Cs fountains. Finally we give an update on the cold atom space clock PHARAO developed in collaboration with CNES. This clock is one of the main instruments of the ACES/ESA mission which is scheduled to fly on board the International Space Station in 2008, enabling a new generation of relativity tests.

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Section: Einstein Equivalence Principle and Stability Of Fundamental mentioning

confidence: 99%

Cold atom clocks and applications

Bize

Laurent

Abgrall

et al. 2005

J. Phys. B: At. Mol. Opt. Phys.

226

161

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“…Optical frequency combs (OFCs) are nowadays used in many applications including optical frequency metrology [1], lowphase-noise microwave generation [2,3], calibration of astronomical spectra [4] and searches for variations of fundamental constants [5,6]. For all of these applications, in which high frequency stability is requested, a simultaneous control of the two degrees of freedom of the OFC, the laser carrier-envelope offset frequency (CEO) f CEO and the repetition rate frequency f rep , are demanded.…”

Section: Introductionmentioning

confidence: 99%

Frequency noise performances of a Ti:sapphire optical frequency comb stabilized to an optical reference

Sutyrin

Poli

Beverini

et al. 2013

Optics Communications

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a b s t r a c tWe report on a detailed analysis of frequency noise and intensity dynamics of a free-running femtosecond Ti:sapphire optical frequency comb (OFC) pumped by a multi-mode 532 nm laser. We have used these results for phase locking the OFC to a Hz-wide, cavity stabilized, 698 nm semiconductor laser. An analysis of the in-loop error signals and an estimation of Allan deviation indicates a lower limit for the frequency stability of the OFC at the level of $ 5:3 Â 10 À14 for 125 ms integration time comparable with the clock laser frequency stability over the entire OFC spectrum. The noise transfer processes between the pump laser and the Ti:sapphire laser have been studied in detail, comparing the resulting frequency noise of the OFC output spectrum with both a single-mode and a multi-mode pump lasers. In the latter case, we employed a pump beam steering control to maintain an OFC regime with a minimum impact of pump laser amplitude noise on the carrier-envelope offset frequency.

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“…In the development of future optical clocks, considering the high stability ( at 1 s) and expected accuracy , a detailed study of the noise characteristics and possible systematic effects in the transfer between the optical and the radio frequency (RF) ranges is imperative if full confidence in future standards is to be gained. As well as timekeeping, one of the most compelling motivations for the development of advanced optical frequency standards is that their comparison would allow one to search for possible time variations of fundamental constants [3], [4]. For example, laboratory based tests of the stability of the fine structure constant show no time-dependence at the present measurement limit of per year [5], [6], while some astronomical measurements indicate that could have been smaller than its present value by a factor of in the early universe some 10 billion years ago [7].…”

Section: Introductionmentioning

confidence: 99%

International Comparisons of Femtosecond Laser Frequency Combs

Bi²,

Bartels³

et al. 2005

IEEE Trans. Instrum. Meas.

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Abstract-Two types of international comparisons of femtosecond laser frequency combs have been performed in France and the USA. Five combs were involved in the comparisons. Three combs, of which two are transportable, employ nonlinear photonic crystal fiber (PCF) to obtain a wide spectrum covering a full optical octave. The other two are based on broadband femtosecond lasers and require no PCF. The comparisons were performed by counting the optical heterodyne beats between pairs of combs. The frequency agreement among three combs was at the subhertz level in the 563 THz part of the comb spectrum when the combs were referenced to a hydrogen maser. When the combs were referenced to an optical standard, the frequency agreement among four combs was much improved and found to be at the 10 19 level in the spectral range of 333-473 THz. The fact that this result is obtained by five independent measurement systems (combs) strengthens the conclusion that no systematic effects are present at this level.Index Terms-Femtosecond laser, frequency measurement, frequency standards.

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Some possibilities for laboratory searches for variations of fundamental constants

Cited by 46 publications

References 39 publications

Cold atom clocks and applications

Cold atom clocks and applications

Frequency noise performances of a Ti:sapphire optical frequency comb stabilized to an optical reference

International Comparisons of Femtosecond Laser Frequency Combs

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