Quantum reflection at normal incidence

Quantum reflection occurs when an atom reflects from an attractive potential without reaching a classical turning point. Atoms will exhibit quantum reflection from the Casimir-Polder potential of a solid surface at sufficiently low incident velocity. Trapped Bose-Einstein condensates of $^{23}$Na, with peak density $10^{11}-10^{12}$~atoms/cm$^3$, normally incident on a silicon surface exhibited reflectivity of up to $20\%$ for incident velocities of $1-8$~mm/s. We discuss evidence for collective effects when a Bose-Einstein condensate undergoes quantum reflection, the possibility of confining atoms with solid surfaces, and recent experimental results.