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Ultracold Bose-Fermi Mixtures of Metastable Helium (bosefermiHe)
Start date: 01 Sep 2008, End date: 31 Aug 2010 PROJECT  FINISHED 

Experiments using Bose-Einstein condensates (BEC) of ultracold atoms have demonstrated the quantum mechanical similarities between ultracold bosonic atoms and photons of light. In addition, research using ultracold fermionic atoms has shed light on other interesting and/or unsolved phenomena, such as the pairing of electrons in superconductors and the mechanisms of high Tc superconductivity. Helium has both stable bosonic (4He) and fermionic (3He) isotopes that may be cooled to quantum degeneracy in a metastable electronic excited state (He*), thus making it ideally suited for the study of the overlap between the fields of ultracold atomic gases, quantum optics and condensed matter. He* offers a major advantage over other atomic species due to the large internal energy (~20 eV) stored in each atom. Whereas the detection of ultracold atoms typically relies on optical means that are limited in resolution and efficiency, He* atoms dropped onto a microchannel plate are precisely located in time and space due to the de-excitation of their internal energy. In groundbreaking experiments, the bunching of bosonic atoms, a phenomenon predicted for photons, has been observed using bosonic 4He*. Remarkably, the corresponding anti-bunching of fermionic 3He* atoms, with no direct optical analogy, was also observed. Incorporating the capacity to trap and cool fermionic 3He* into an existing 4He* BEC apparatus will open the door to many new opportunities. For example, bosons within a Bose-Fermi mixture may mediate interactions between fermions and play the role of the phonons in a BCS superconductor. Moreover, Bose-Fermi mixtures in optical lattices promise a unique opportunity for the study of condensed matter systems, and the detection capability afforded by the He* system should allow for the observation of correlations and possibly quantum entanglement.
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