Testing General Relativity with Atomic Clocks

Reynaud, Serge; Salomon, Christophe; Wolf, Peter

doi:10.1007/s11214-009-9539-0

Cited by 48 publications

(20 citation statements)

References 82 publications

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“…The Atomic Clock Ensemble in Space (ACES) project will place both a cold trapped atom clock based on Cesium called PHARAO (Projet d’Horloge Atomique par Refroidissement d’Atomes en Orbite), and an advanced hydrogen maser clock on the International Space Station to measure the gravitational redshift to parts in 10 6 , as well as to carry out a number of fundamental physics experiments and to enable improvements in global timekeeping [335]. Launch is currently scheduled for May 2016.…”

Section: Tests Of the Foundations Of Gravitation Theorymentioning

confidence: 99%

The Confrontation between General Relativity and Experiment

Will

2014

Living Rev. Relativ.

2,694

2,346

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The status of experimental tests of general relativity and of theoretical frameworks for analyzing them is reviewed and updated. Einstein’s equivalence principle (EEP) is well supported by experiments such as the Eötvös experiment, tests of local Lorentz invariance and clock experiments. Ongoing tests of EEP and of the inverse square law are searching for new interactions arising from unification or quantum gravity. Tests of general relativity at the post-Newtonian level have reached high precision, including the light deflection, the Shapiro time delay, the perihelion advance of Mercury, the Nordtvedt effect in lunar motion, and frame-dragging. Gravitational wave damping has been detected in an amount that agrees with general relativity to better than half a percent using the Hulse-Taylor binary pulsar, and a growing family of other binary pulsar systems is yielding new tests, especially of strong-field effects. Current and future tests of relativity will center on strong gravity and gravitational waves.

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Section: Tests Of the Foundations Of Gravitation Theorymentioning

confidence: 99%

The Confrontation between General Relativity and Experiment

Will

2014

Living Rev. Relativ.

2,694

2,346

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“…Optical-frequency comparisons between a pattern of spectral holes, a Fabry-Pérot cavity, and an Al + optical atomic clock show a short-term fractional frequency stability of 1 × 10 −15 τ −1/2 that averages down to 2.5 Frequency-stable laser local oscillators (LLOs) are important tools for a variety of precision measurements. Examples include both scientific applications such as searches for the variation of fundamental constants [1,2] and tests of general relativity [3,4] as well as technical applications such as synthesis of low-phase-noise microwaves [5][6][7] and relativistic geodesy [8,9]. The stability of the best lasers constructed to date [10][11][12] is limited by thermomechanical length fluctuations of the Fabry-Pérot reference cavities used for stabilization (i.e., thermally-driven displacement fluctuations of the atoms that make up the cavity) [13,14].…”

mentioning

confidence: 99%

Absolute and Relative Stability of an Optical Frequency Reference Based on Spectral Hole Burning inEu3+:Y2SiO5

et al. 2013

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We present and analyze four frequency measurements designed to characterize the performance of an optical frequency reference based on spectral hole burning in Eu 3+ :Y2SiO5 . The first frequency comparison, between a single unperturbed spectral hole and a hydrogen maser, demonstrates a fractional frequency drift rate of 5 × 10 −18 s −1 . Optical-frequency comparisons between a pattern of spectral holes, a Fabry-Pérot cavity, and an Al + optical atomic clock show a short-term fractional frequency stability of 1 × 10 −15 τ −1/2 that averages down to 2.5 Frequency-stable laser local oscillators (LLOs) are important tools for a variety of precision measurements. Examples include both scientific applications such as searches for the variation of fundamental constants [1,2] and tests of general relativity [3,4] as well as technical applications such as synthesis of low-phase-noise microwaves [5][6][7] and relativistic geodesy [8,9]. The stability of the best lasers constructed to date [10][11][12] is limited by thermomechanical length fluctuations of the Fabry-Pérot reference cavities used for stabilization (i.e., thermally-driven displacement fluctuations of the atoms that make up the cavity) [13,14]. Present and future applications would benefit from lasers with improved stability [12,15].One alternative to the mechanical frequency reference provided by Fabry-Pérot cavities is spectral-hole burning (SHB) laser-frequency stabilization [16][17][18][19][20]. In this technique, the frequency reference is an atomic transition of rare-earth dopant ions in a cryogenically cooled crystal. These systems typically display an inhomogeneously broadened absorption line with a linewidth of order gigahertz, but the optical coherence time can be as long as milliseconds. Thus, in systems with an appropriate level structure, a spectrally-narrow transparency, or spectral hole, can be written into the broad absorption line by optically pumping a subset of the dopant ions to a longlived auxiliary state. For laser-frequency stabilization, a spectral hole is written into the crystal at the beginning of the experiment, and subsequently the laser frequency is stabilized to the center of the spectral hole by probing the transmission of the crystal and feeding back to the laser frequency. Because the coupling between crystal strain and the internal states of the dopant ions is weak, the thermomechanical noise that limits Fabry-Pérot cavities is only a weak perturbation to the frequencies of spectral holes.The material system Eu 3+ :Y 2 SiO 5 in particular is very promising for high-performance laser-frequency stabilization because it supports spectral holes with a linewidth

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“…It represents an aspect of the Einstein Equivalence Principle (EEP) often referred to as Local Position Invariance (LPI) [117], and it makes clocks direct probes of the gravitational potential (and thus to the metric tensor g 00 component). In GR, the frequency difference of two ideal clocks is proportional to [92]…”

Section: Gravitational Potentialmentioning

confidence: 99%

The local dark sector

Bergé

Baudis²,

Brax

et al. 2021

Exp Astron

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We speculate on the development and availability of new innovative propulsion techniques in the 2040s, that will allow us to fly a spacecraft outside the Solar System (at 150 AU and more) in a reasonable amount of time, in order to directly probe our (gravitational) Solar System neighborhood and answer pressing questions regarding the dark sector (dark energy and dark matter). We identify two closely related main science goals, as well as secondary objectives that could be fulfilled by a mission dedicated to probing the local dark sector: (i) begin the exploration of gravitation’s low-acceleration regime with a spacecraft and (ii) improve our knowledge of the local dark matter and baryon densities. Those questions can be answered by directly measuring the gravitational potential with an atomic clock on-board a spacecraft on an outbound Solar System orbit, and by comparing the spacecraft’s trajectory with that predicted by General Relativity through the combination of ranging data and the in-situ measurement (and correction) of non-gravitational accelerations with an on-board accelerometer. Despite a wealth of new experiments getting online in the near future, that will bring new knowledge about the dark sector, it is very unlikely that those science questions will be closed in the next two decades. More importantly, it is likely that it will be even more urgent than currently to answer them. Tracking a spacecraft carrying a clock and an accelerometer as it leaves the Solar System may well be the easiest and fastest way to directly probe our dark environment.

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Testing General Relativity with Atomic Clocks

Cited by 48 publications

References 82 publications

The Confrontation between General Relativity and Experiment

The Confrontation between General Relativity and Experiment

Absolute and Relative Stability of an Optical Frequency Reference Based on Spectral Hole Burning inEu3+:Y2SiO5

The local dark sector

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