Superposition

  • Flying Optical Cats for Quantum Communication

    An atom is trapped in the resonator between two mirrors (left). A reflected light pulse gets entangled with the atom and may fly freely as a superimposed cat state (right). Bastian Hacker, Max Planck Institute of Quantum Optics (MPQ)

    Dead and alive at the same time? Researchers at the Max Planck Institute of Quantum Optics have implemented Erwin Schrödinger’s paradoxical gedanken experiment employing an entangled atom-light state. In 1935 Erwin Schrödinger formulated a thought experiment designed to capture the paradoxical nature of quantum physics. The crucial element of this gedanken experiment is a cat that is simultaneously dead and alive. Since Schrödinger proposed his ‘cat paradox’, physicists have been thinking about ways to create such superposition states experimentally.

  • Ultracold atoms in a "Rydberg-dress"

    Ultracold atoms in a Rydberg dress picture1 | Fig. 1: From the starting state densely filled with atoms (left), a ring-like structure emerges due to the long range interaction (right). Graphic: MPQ, Quantum Many-Body Systems Division

    Scientists at the MPQ (Garching) and MPIPKS (Dresden) have developed a novel technique to let atoms interact over large distances.

    Many properties of our everyday world can be explained if atoms are thought of as small, solid marbles, which feel each other only if brought in direct contact with each other. The temperature of the air surrounding us, for example, is the result of uncountable, continuously occurring collisions between its constituents. Contrary to this, we also know effects which arise from the interplay between two distant objects. Well-known examples are two magnets which can affect each other also at quite a distance, or the formation of a salt crystal as a regular arrangement of positively charged sodium and negatively charged chlorine ions, which are bound together at large distances by electrical attraction.