  Femtosecond coherent multidimensional spectroscopy is demonstrated for an
ultracold gas. For this, a setup for phase modulation spectroscopy is used to
probe the $3^2\mathrm{S}_{1/2} - 2^2\mathrm{P}_{1/2, 3/2}$ transition in an 800
$\mu$K-cold sample of $^7$Li atoms confined in a magneto-optical trap. The
observation of a double quantum coherence response, a signature of
interparticle interactions, paves the way for detailed investigations of few-
and many-body effects in ultracold atomic and molecular gases using this
technique. The experiment combines a frequency resolution of 3 GHz with a
potential time resolution of 200 fs, which allows for high-resolution studies
of ultracold atoms and molecules both in the frequency and in the time domain.
