Universal Loss Dynamics of a Degenerate Homogeneous Unitary Bose Gas

We study the loss dynamics of a degenerate $^{39}$K Bose gas confined in an optical box trap. Starting with a quasi-pure Bose-Einstein condensate in the Thomas-Fermi regime, where the density $n$ is uniform, we quench the scattering length $a$ to the unitary regime, where $a$ diverges. Observing the cloud after a variable hold time at unitarity directly reveals a loss rate which is dictated solely by the density of the cloud and scales as $n^{\frac{2}{3}}$. This is in stark contrast to measurements performed away from unitarity, where the more conventional $n^{2}$ scaling is observed. Our measurements also provide insight into the time evolution of the momentum distribution at unitarity.