Deterministic preparation of a tunable few-fermion system.

Systems consisting of few interacting fermions are the building blocks of matter, with atoms and nuclei being the most prominent examples. We have created a few-body quantum system with complete control over its quantum state using ultracold fermionic atoms in an optical dipole trap. Ground-state systems consisting of 1 to 10 particles are prepared with fidelities of ∼90%.

Radio-frequency association of Efimov trimers.

The quantum mechanical three-body problem is one of the fundamental challenges of few-body physics. When the two-body interactions become resonant, an infinite series of universal three-body bound states is predicted to occur, whose properties are determined by the strength of the two-body interactions. We used radio-frequency fields to associate Efimov trimers consisting of three distinguishable fermions.

Atom-dimer scattering in a three-component Fermi gas.

Ultracold gases of three distinguishable particles with large scattering lengths are expected to show rich few-body physics related to the Efimov effect. We have created three different mixtures of ultracold 6Li atoms and weakly bound 6Li2 dimers consisting of atoms in three different hyperfine states and studied their inelastic decay via atom-dimer collisions. We have found resonant enhancement of the decay due to the crossing of Efimov-like trimer states with the atom-dimer continuum in one mixture as well as minima of the decay in another mixture, which we interpret as a suppression of exchange reactions of the type |12+|3→|23+|1.

Collisional stability of a three-component degenerate fermi gas.

We report on the creation of a degenerate Fermi gas consisting of a balanced mixture of atoms in three different hyperfine states of 6Li. This new system consists of three distinguishable fermions with different and tunable interparticle scattering lengths a_{12}, a_{13}, and a_{23}. We are able to prepare samples containing 5x10;{4} atoms in each state at a temperature of about 215 nK, which corresponds to T/T_{F} approximately 0.