Speaker
Description
At very low transversal energies, light neutral particles above a horizontal reflective surface can undergo quantum reflection forming gravitational quantum states (GQS). While these states have been experimentally observed only for neutrons in 2002 by V.V. Nesvizhevsky et al., theory predicts their existence also for atoms. GQS provide a sensitive probe for new fundamental short-range interactions predicted in extensions of the Standard Model and in models explaining dark matter and dark energy [1;2].
In the far field, interference of quantum states emerges, providing a powerful tool for high-sensitivity measurements. Small shifts in the interference pattern can arise from external interactions. While gravity induces a mass-dependent shift, unknown interactions would produce additional deviations. In contrast to GQS transmission measurements, which primarily confirm the existence of such states, far field interference measurements enable substantially higher precision and allow surface-dependent short-range interactions to be probed and constrained [3].
We present the current state of preparation for far field measurements of GQS of atomic hydrogen in Vienna. The experiment utilizes a cryogenic beam with low horizontal velocities. To measure the GQS, a one-component gravitational spectrometer is used. This spectrometer consists of a flat mirror on the bottom and a macroscopically flat scatterer on top separated by a gap of variable size $h$. The preparations for the first measurements of GQS with atomic hydrogen and for the far field measurements are ongoing.
References
[1] C. Killian et al. GRASIAN: towards the first demonstration of gravitational quantum
states of atoms with a cryogenic hydrogen beam. The European Physical Journal D, (3), 2023. doi: 10.1140/epjd/s10053-023-00634-4.
[2] V. V. Nesvizhevsky et al. Quantum states of neutrons in the earth’s gravitational field. Nature, 2002. doi: 10.1038/415297a.
[3] V. V. Nesvizhevsky et al. Gravitational and other shifts of whispering gallery and gravitational state interference patterns of light neutral particles, 2025.