Abstract
A double atom interferometer based upon the Stern-Gerlach method in which the first interferometer acts as a "nonordinary" source for the second one is described. Experiments have been carried out with a wide-velocity-distribution beam of metastable hydrogen atoms, using two different operating modes: (i) continuous mode in which the magnitude of the magnetic field in the first interferometer is fixed whereas that of the second one is scanned; (ii) time-of-flight mode in which both magnetic fields are fixed. In the former case lateral interference patterns appear, in the latter one an overmodulation of the time-of-flight distribution is observed. It is predicted that this overmodulation becomes more and more marked as the number of interferometers is increased, leading to a limiting behavior characteristic of a quantum Zeno effect. [S1050-2947(98)01811-3].