A commentary on the Nobel Prize in Physics

At the turn of the 20th century, a number of discoveries were made in the physics of the micro-world that could not be explained within the framework of the science of the time. This led to a new theory - quantum mechanics. Its principles and the phenomena it predicts are so different from the laws of classical physics describing the world observed every day on a macroscopic scale that they appear absurd but are confirmed experimentally.

The 2022 Nobel Prize in Physics has been awarded to three scientists working on experimental and theoretical aspects of quantum mechanics. As set out in the verdict of the Royal Swedish Academy of Sciences, the prize was awarded "for experiments with entangled photons, establishing violations of Bell's inequality and pioneering quantum computing".

The award winners are: Alain Aspect of Université Paris-Saclay and École Polytechnique, Palaiseau, France, John F. Clauser of J. F. Clauser & Assoc., Walnut Creek, CA USA and Anton Zeilinger of the Universität Wien, Austria.

The amount of the prize is SEK 10 million, to be divided equally between the winners.

"Entanglement" is one of the phenomena occurring in the world of microparticles, which is governed by the laws of quantum mechanics.  It relies on the fact that there is a bond between two particles that makes them behave as a single object, no matter how far apart they are. Consequently, what happens to one particle of an entangled pair affects the properties of the other.

Alain Aspect, John Clauser and Anton Zeilinger conducted groundbreaking experiments with photons on such entangled quantum states. The existence of entanglement between photons more than 100 km apart has been demonstrated. These experiments demonstrated a violation of the aforementioned 'Bell's inequality' associated with the description of microscopic phenomena using so-called 'hidden variables' and proved that nature behaves as predicted by quantum mechanics and that a theory using hidden variables cannot be an alternative to quantum mechanics.

These experiments are the basis of the revolution that is now taking place and leading to the emergence of quantum technology, in which effects described by quantum mechanics are beginning to be applied. This is the second revolution as a consequence of quantum mechanics. The fruits of the first are semiconductor-based devices, for example transistors and lasers. A vast field of research into entangled states - quantum computing - is now developing, including quantum computers, quantum internet networks and secure encrypted quantum communication and also a phenomenon called quantum teleportation, which allows the transfer of a quantum state from one particle to another over any distance using an entangled state.