Entangled states
Interference patterns are a crucial signature that a quantum gas has been confined in an optical lattice. After applying a quantum-gate array for different lengths of time the many-body state of the atoms (left) evolves into an entangled state, for which no interference pattern can be observed, and back to a disentangled state (right), for which an interference pattern can again be seen. This periodic evolution of the many-body system demonstrates the full coherence of the controlled collisions that were introduced between the atoms. The images represent the density distribution of the expanding atoms after they have been released from the lattice potential. A high peak denotes a high column density, which has also been encoded into a corresponding colour.