Entangled photons are created here by a laser that is sent into a crystal with special optical properties. A small part of the laser light fans out into two cones of different polarization. The photons that fly exactly along the two intersection lines of the cones – in this cross-section the intersection points of the circles – are then entangled with each other.
Image: IQOQI/ Paul Kwiat and Michael Reck
The Nobel Committee honors experiments with startling philosophical consequences. How mandatory are they?
Einstein was wrong. It is this finding that brought John Clauser, Alain Aspect and Anton Zeilinger this year’s Nobel Prize in Physics. Before everyone gets confused who regularly reads about new confirmations for Albert Einstein’s theory of relativity: That’s not the point. It’s about quantum theory.
Einstein did not want to believe in it – at least not in the form in which it was developed in the 1920s and mathematically codified in its foundations at the beginning of the 1930s – foundations that also form the basis of later further developments, up to the current efforts to generalize them to a theory of quantum gravity. And on these foundations, quantum theory is amazingly successful: Everything microscopic – molecules, atoms, elementary particles – and also much macroscopic things, from lasers to superconductors, have to be calculated with their equations, otherwise what is observed does not come out or not exactly what is observed. But does that mean that the principles of quantum theory are correct?