(a) APS/Alan Stonebraker, based on sketch by Mark Kasevich, Stanford University; (b) and (c) adapted from S.-W. Chiow et al. [2]

Figure 1: (a) A Bose Einstein condensate is vertically launched in the vacuum chamber and exposed to a series of coherent manipulation processes. (b) Carefully chosen pulse sequences result in division into two separate wave packets (the “beam splitter”), swapping the momentum states of the two emerging partial wave packets (the “atom mirror”), and recombination by a second “beam splitter”, identical to the first one. (c) All three optical elements can be achieved by a combination of two judiciously tuned vertically counterpropagating laser beams (f1 and f2), which transfer the momentum of six photons per pulse onto the atoms. The $102ħk$ interferometer consists of $17$ such pulses in a single beam splitter sequence and up to $33$ pulses to realize the mirror. The laser intensity determines whether the light acts as a beam splitter or a mirror. The location of the atomic wave packets at the interrogation time can be visualized by detecting the shadow images on a CCD camera when the atoms are illuminated by resonant laser light from the side.