Decoherence of a matter wave by blackbody radiation

We have observed the decoherence of a lithium atomic wave during its propagation in the presence of theradiation emitted by tungsten-halogen lamps, i.e., decoherence induced by blackbody radiation. We used ouratom interferometer to detect this decoherence by measuring the atom fringe-visibility loss. The absorption of aphoton excites the atom, which spontaneously emits a fluorescence photon. The momenta of these two photonshave random directions, and this random character is the main source of decoherence. All previous similarexperiments used small-bandwidth coherent excitation by a laser, whereas incoherent radiation involves severaltechnical and conceptual differences. Our approach is interesting as blackbody radiation is omnipresent anddecoherence should be considered if particles resonant to electromagnetic fields are used.