Advances in the measurement of gravity-induced quantum phase shifts

One of the significant successes in the field of neutron interferometry has been the experimental observation of the phase shift of a neutron deBroglie wave due to the action of the Earth's gravitational field. In this experiment the gravity-induced phase shift of the neutron is measured with a statistical uncertainity of order 1 part in 1000 in two different interferometers using nearly harmonic pairs of neutron wavelengths in two different interferometers. Extensions of the theoretical description of the tilt-angle gravity interferogram are discussed. A discrepancy between the theory and measured values of the phase shift due to gravity is observed at the 1% level.