New test of the weak equivalence principle for neutrons

We describe a neutron gravity quantum experiment of a new type. The gain in kinetic energy of free-falling neutrons is compensated by a quantum of energy h a due to phase modulation of the neutron wave. As phase modulator a grating was used moving perpendicular with respect to the direction of the neutron wave propagation. As a result, monochromatic neutrons will have exactly the same energy after falling as before the free fall. The weak equivalence principle was tested to an accuracy of 2 x 10(-3). A possible future experiment of more improved accuracy is discussed as well. (C) 2009 Elsevier B.V. All rights reserved.