Qualification and frequency accuracy of the space-based primary frequency standard PHARAO

Laurent, Ph.; Esnaut, F. X.; Gibble, Kurt; Peterman, P.; Lévèque, Thomas; Delaroche, C.; Grosjean, Olivier; Moric, Igor; Abgrall, M.; Massonnet, D.; Salomon, C.

doi:10.1088/1681-7575/ab948b

Cited by 5 publications

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Scalar gravitational Aharonov–Bohm effect: Generalization of the gravitational redshift

Tobar,

Hatzon,

Flower

et al. 2024

Applied Physics Letters

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The Aharonov–Bohm effect is a quantum mechanical phenomenon that demonstrates how potentials can have observable effects even when the classical fields associated with those potentials are absent. Initially proposed for electromagnetic interactions, this effect has been experimentally confirmed and extensively studied over the years. More recently, the effect has been observed in the context of gravitational interactions using atom interferometry. Additionally, recent predictions suggest that temporal variations in the phase of an electron wave function will induce modulation sidebands in the energy levels of an atomic clock, solely driven by a time-varying scalar gravitational potential. In this study, we consider the atomic clock as a two-level system undergoing continuous Rabi oscillations between the electron's ground and excited state. We assume the photons driving the transition are precisely frequency-stabilized to match the transition, enabling accurate clock comparisons. Our analysis takes into account, that when an atom transitions from its ground state to an excited state, it absorbs energy, increasing its mass according to the mass-energy equivalence principle. Due to the mass difference between the two energy levels, we predict that an atomic clock in an eccentric orbit experiencing a time-varying gravitational potential, will exhibit a constant frequency redshift relative to a ground clock, corresponding to the orbit's average gravitational redshift. Additionally, modulation sidebands will appear, and detecting these predicted sidebands would confirm the scalar gravitational Aharonov–Bohm effect.

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Scalar gravitational Aharonov–Bohm effect: Generalization of the gravitational redshift

Tobar,

Hatzon,

Flower

et al. 2024

Applied Physics Letters

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Atomic Clock Ensemble in Space

Cacciapuoti,

Busso,

Jansen

et al. 2024

J. Phys.: Conf. Ser.

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The Atomic Clock Ensemble in Space (ACES) mission is developing high performance clocks and links for space to test Einstein’s theory of general relativity. From the International Space Station, the ACES payload will distribute a clock signal with fractional frequency stability and accuracy of 1 × 10−16 establishing a worldwide network to compare clocks in space and on the ground. ACES will provide an absolute measurement of Einstein’s gravitational redshift, it will search for time variations of fundamental constants, contribute to test topological dark matter models, and perform Standard Model Extension tests. Moreover, the ground clocks connected to the ACES network will be compared over different continents and used to measure geopotential differences at the clock locations. After solving some technical problems, the ACES flight model is now approaching its completion. System tests involving the laser-cooled Cs clock PHARAO, the active H-maser SHM and the on-board frequency comparator FCDP have measured the performance of the clock signal delivered by ACES. The ACES microwave link MWL is currently under test. The single-photon avalanche detector of the optical link ELT has been tested and will now be integrated in the ACES payload. The ACES mission concept, its scientific objectives, and the recent test results are discussed here together with the major milestones that will lead us to the ACES launch.

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