We discuss the effect of interatomic interactions on the condensation temperature
Tc of a laboratory atomic Bose-Einstein condensate under the influence of an external trapping magnetic field. We predict that accounting for hyperfine interactions mediated Zeeman term in the mean-field approximation produces, in the case of the
403G Feshbach resonance in the
∣F,mF>=∣1,1> hyperfine state of a
39K condensate, with
F the total spin of the atom, an experimentally observed (and not yet explained) shift in the condensation temperature
ΔTc/Tc0=b0∗+b1∗(a/λT)+b2∗(a/λT)2 with
b0∗≃0.0002,
b1∗≃−3.4 and
b2∗≃47, where
a is the s-wave scattering length, and
λT is the thermal wavelength at
Tc0. Generic expressions for the coefficients
b0∗,
b1∗ and
b2∗ are also obtained, which can be used to predict the temperature shift for other Feshbach resonances of
39K or other atomic condensates.
A Bose–Einstein trap Until now, quantum atomic gases and single trapped ions have been treated separately in experiments. Now a team from the Cavendish Laboratory in Cambridge has combined the two, in the form of a hybrid quantum system composed of a Bose–Einstein condensate of neutral atoms and a trapped atomic ion. They achieve independent control over the two systems, study the fundamental interaction processes and observe sympathetic cooling of the single ion by the condensate. Possible avenues of research that this could lead to include the continuous cooling of quantum computers, and explorations of entanglement in hybrid quantum systems.