Matterwave Phase Doubling in Quantum Many-Body Chemistry

One of the defining features of quantum mechanics is the phase of the wavefunction. Bose-Einstein condensates (BEC) can be described as macroscopic matterwaves that contain the phase information. In this work, we demonstrate phase doubling when Bose condensed atoms are paired into diatomic molecules. This phenomena is the matterwave equivalent of second harmonic generation in nonlinear optics. To show the phase doubling, we first imprint a phase pattern onto the atomic BEC using an optical lattice and then pair the atoms into molecules. By imaging the molecules after time-of-flight, we can see how the phase evolves from the diffraction of molecules to different momentum modes. Our research demonstrates the essential role of matterwave phase in quantum many-body chemistry.