Experimenters Cool Helium Below Single‐Photon Recoil Limit in Three Dimensions
DOI: 10.1063/1.2807458
A group at the Ecole Normale Superieure in Paris has placed a helium atom in a state that is going in six directions at once—a very confusing state for an atom. In such a superposition state, also called a dark state, the atom can’t absorb light because the absorption amplitudes cancel out by destructive interference. The temperature corresponding to the velocity spread of each of the six wavepackets is a factor of 20 below the so‐called recoil limit for laser‐cooled atoms. The three‐dimensional subrecoil experiment in helium was reported in the 4 December issue of Physical Review Letters by John La wall (now at the National Institute of Standards and Technology in Gaithersburg, Maryland), Si‐mone Kulin, Bruno Saubamea, Nick Bigelow, Michèle Leduc and Claude Cohen‐Tannoudji.
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