Neutron quantum states

The existence of quantum states of matter in the gravitational field has been demonstrated for the very first time at the ILL by a series of ground-breaking experiments [1-3] with ultracold neutrons (UCN).

The animation shows the principle of the experiment. This made use of ultra cold neutrons (UCNs) bouncing on the surface of a mirror and selected so that their vertical speed is extremely low. The neutrons are confined in a well with gravity the attractive force (neutrons fall on the surface of the mirror) and repulsion by the mirror surface (UCNs cannot penetrate matter) the opposite force.
This experiment demonstrated that, in such specific conditions, energy levels are well separated with neutron quantum states exhibiting macroscopic sizes (about 10 µm).
The gravitational spectrometer GRANIT is the follow-up project based on a second-generation UCN gravitational spectrometer with ultra-high energy resolution.

1- V.V.Nesvizhevsky, H.G.Börner, A.K.Petukhov, H.Abele, S.Baeβler, F.J.Rueβ, Th.Stöferle, A.Westphal, A.M.Gagarsky, G.A.Petrov, and A.V.Strelkov (2002). "Quantum states of neutrons in the Earth's gravitational field." Nature 415: 297-299. Doi:10.1038/415297a
2- V.V.Nesvizhevsky, H.G.Börner, A.M.Gagarski, A.K.Petukhov, G.A.Petrov, H.Abele, S.Baeßler, G.Divkovic, F.J.Rueß, T.Stöferle, A.Westphal, A.V.Strelkov, K.V.Protasov, A.Yu.Voronin (2003). "Measurement of quantum states of neutrons in the Earth's gravitational field." Physical Review D 67: 102002(1-9). Doi:10.1103/PhysRevD.67.102002
3- V.V.Nesvizhevsky, A.K.Petukhov, H.G.Börner, T.A.Baranova, A.M.Gagarski, G.A.Petrov, K.V.Protasov, A.Yu.Voronin, S.Bäßler, H.Abele, A.Westphal, and L.Lucovac (2005). "Study of the neutron quantum states in the gravity field." European Physical Journal C 40(4): 479-491. Doi:10.1140/epjc/s2005-02135-y