Spectroscopic measurement of the Casimir-Polder force in the intermediate regime

Fuente: arXiv
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Main Authors: Ton, K., Kestler, G., Steck, D. A., Barreiro, J. T.
Format: Preprint
Published: 2026
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author Ton, K.
Kestler, G.
Steck, D. A.
Barreiro, J. T.
author_facet Ton, K.
Kestler, G.
Steck, D. A.
Barreiro, J. T.
contents The Casimir-Polder (CP) effect -- the force between a neutral atom and an uncharged conducting plate in empty space -- is an intriguing consequence of quantum vacuum fluctuations. The typically attractive CP potential crosses over from a scaling of $z^{-3}$ at short separations to $z^{-4}$ at long distances, where retardation effects due to the finite speed of light become important. At intermediate distances, where the atom--surface separation is of the order of the wavelength of the dominant atomic transition, experiments have so far relied on indirect methods, such as diffraction or quantum reflection, to observe the CP effect. Here, we directly reveal the CP force between strontium atoms and a dielectric surface via the induced shifts in the atomic energy levels in the intermediate regime. We spectroscopically probe the CP-induced kHz-frequency shift of ultracold atoms confined by a magic-wavelength optical lattice at 189(2)~nm from the surface -- on the scale of the dominant 461-nm transition. Our measurements agree well with QED calculations and differ from the short-range approximation, while excluding the long-distance one. This paves the way for studying the CP effect across various surface properties and geometries, as well as exploring the tensor nature of the atom-surface potential -- all important for the development of hybrid atomic optical-magnetic quantum devices.
format Preprint
id arxiv_https___arxiv_org_abs_2604_14721
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle Spectroscopic measurement of the Casimir-Polder force in the intermediate regime
Ton, K.
Kestler, G.
Steck, D. A.
Barreiro, J. T.
Quantum Physics
Quantum Gases
Atomic Physics
The Casimir-Polder (CP) effect -- the force between a neutral atom and an uncharged conducting plate in empty space -- is an intriguing consequence of quantum vacuum fluctuations. The typically attractive CP potential crosses over from a scaling of $z^{-3}$ at short separations to $z^{-4}$ at long distances, where retardation effects due to the finite speed of light become important. At intermediate distances, where the atom--surface separation is of the order of the wavelength of the dominant atomic transition, experiments have so far relied on indirect methods, such as diffraction or quantum reflection, to observe the CP effect. Here, we directly reveal the CP force between strontium atoms and a dielectric surface via the induced shifts in the atomic energy levels in the intermediate regime. We spectroscopically probe the CP-induced kHz-frequency shift of ultracold atoms confined by a magic-wavelength optical lattice at 189(2)~nm from the surface -- on the scale of the dominant 461-nm transition. Our measurements agree well with QED calculations and differ from the short-range approximation, while excluding the long-distance one. This paves the way for studying the CP effect across various surface properties and geometries, as well as exploring the tensor nature of the atom-surface potential -- all important for the development of hybrid atomic optical-magnetic quantum devices.
title Spectroscopic measurement of the Casimir-Polder force in the intermediate regime
topic Quantum Physics
Quantum Gases
Atomic Physics
url https://arxiv.org/abs/2604.14721