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Single spontaneous photon as a coherent beamsplitter for an atomic matter-wave

Tue, 2011-10-18 14:46 - Donatella Rosetti
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Date: 
2011-04-03
Author(s): 

J. Tomkovic, M. Schreiber, J. Welte, M. Kiffner, H.-J. Schmiedmayer, M.K. Oberthaler

Reference: 

Nature Physics, (2011), pp. 1 - 8
doi: 10.1038/NPHYS1961

In spontaneous emission an atom in an excited state undergoes a transition to the ground state and emits a single photon. Associated with the emission is a change of the atomic momentum due to photon recoil. Photon emission can be modified close to surfaces and in cavities. For an ion, localized in front of a mirror, coherence of the emitted resonance fluorescence has been reported. Previous experiments demonstrated that spontaneous emission destroys motional coherence. Here we report on motional coherence created by a single spontaneous emission event close to a mirror surface. The coherence in the free atomic motion is verified by atom interferometry. The photon can be regarded as a beamsplitter for an atomic matter-wave and consequently our experiment extends the original recoiling slit Gedanken experiment by Einstein to the case where the slit is in a robust coherent superposition of the two recoils associated with the two paths of the quanta.