quantum superpositions tagged posts

Interferometric visibility and coherence. Proceedings of the Royal Society A: Mathematical, Physical and Engineering Science, 2017; 473 (2203): 20170170 DOI: 10.1098/rspa.2017.0170

One of the main principles of quantum physics is the superposition of states. Systems are simultaneously in different states, i.e. “alive and dead” at the same time such as Schrödinger’s cat, until someone measures them and the system opts for one of the possibilities. As long as the superposition lasts the system is said to be in a coherent state...

There are two different ways the helium atom can be ionized.

Scientists have observed how quantum superpositions build up in a helium atom within femtoseconds. Just like the two paths through the plate in the double slit experiment, the ionization of helium can happen via 2 different processes at the same time, and this leads to characteristic interference effects. In the case of the helium atom, they are called “Fano resonances.” A team from TU Wien (Vienna), Max-Planck Institute for Nuclear Physics in Heidelberg and Kansas State University has now managed to observe the buildup up of these Fano resonances.

When a laser pulse transfers enough energy to one of the electrons in the helium atom, the electron is ripped out of the atom right away...