No example is available for this instrument since it is not yet commissioned. However, the validity of the assumptions on which the design of GRANIT relies was demonstrated by an experiment performed on the reflectometer D17 in 2009 (see below).

The "whispering gallery" effect has been known since ancient times for sound waves in air, later in water and more recently for a broad range of electromagnetic waves: radio, optics, Roentgen and so on. It consists of wave localization near a curved reflecting surface and is expected for waves of various natures, for instance, for atoms and neutrons. For matter waves, it would include a new feature: a massive particle would be settled in quantum states, with parameters depending on its mass.

Here, we present for the first time the quantum whispering-gallery effect for cold neutrons observed on the reflectometer D17. This phenomenon provides an example of an exactly solvable problem analogous to the ‘quantum bouncer’ ; it is complementary to the recently discovered gravitationally bound quantum states of neutrons. These two phenomena provide a direct demonstration of the weak equivalence principle for a massive particle in a pure quantum state.

Deeply bound whispering-gallery states are long-living and weakly sensitive to surface potential; highly excited states are short-living and very sensitive to 
the wall potential shape. Therefore, they are a promising tool for studying fundamental neutron–matter interactions, quantum neutron optics and surface physics effects.

Ref.: V.V. Nesvizhevsky, A.Yu. Voronin, R. Cubitt and K.V. Protasov (2009) Nature physics, in the press.