Q-BOUNCE—Experiments with quantum bouncing ultracold neutrons

Measuring the dynamics of a quantum mechanical wave packet bouncing off a hard surface in the earth's gravitational field offers the possibility of observing quantum phenomena such as collapses and revivals of the wave function. As it combines quantum theory with aspects of Newtonian mechanics, such a system is highly sensitive on tests of Newton's inverse square law of gravity at small distances and other hypothetical Yukawa-like interactions like the pseudo-scalar coupling of axions. The experiment can therefore test speculations on large, sub-millimeter sized extra dimensions of space–time and the cosmological constant in the universe, where effects are predicted in the interesting range of the experiment. We present first experimental results on such a quantum bouncing ball.