NOf course, the question of the benefit was also asked straight away. And so physicist Eva Olsson of Chalmers University in Gothenburg, as a member of the Nobel Prize Committee, began her summary of yesterday’s decision by her panel to award the 2022 Nobel Prize in Physics equally to Frenchman Alain Aspect, American John Clauser and Austrian Anton Zeilinger with relevant keywords: “Quantum information science has potential implications for fields such as secure information transfer, quantum computing and sensor technology.”
And it’s true. In particular, Anton Zeilinger’s life’s work has turned what seemed an obscure niche of theoretical physics to the broader public, into a subject with rapidly growing sub-disciplines, some of which are in the process of morphing into engineering sciences, also in view of their practical and commercial promises.
At the heart of all of this effort is an effect called “quantum entanglement.” If two things in nature, for the description of which quantum theory has to be used – for example two light photons or subatomic particles – are entangled, then they can only be described together. Nothing can then be said about the behavior of one without the other, no matter how far apart the two are. Mathematically, this is a consequence and not a postulate of quantum theory. However, one of its pioneers, Zeilinger’s compatriot Erwin Schrödinger, wrote in 1935 that entanglement was not one of the theory’s characteristic properties, but its characteristic.
Making the entanglement technically available is the most convincing proof imaginable of its reality. But this year’s Nobel Prize also recognizes an achievement that goes much deeper: the experimental physical, and therefore strictly empirical, proof that quantum theory must be correct in itself.
For also around 1935, a controversy raged about another property of the new theory, as formulated by its founding fathers, including Niels Bohr, Werner Heisenberg and Max Born, which was actually already in its postulates: it is non-deterministic. The only thing that can be derived from the quantum laws is the frequency of different measurement results after repeated measurements. The value of a single measurement, on the other hand, is random.
Is the quantum theory correct and complete?
It is hardly possible to overstate the importance of this statement for our understanding of physical reality. She is heartbreaking. Because it says that the decay of a uranium atom, for example, can only be described statistically. Only the probability with which such an atom has disintegrated after a given period of time is determined by natural laws. However, it is impossible to calculate in advance when this one atom will disintegrate – and thus perhaps cause other events, including macroscopic events, such as the outcome of a lottery draw.
If that uranium atom decays, say, one hour after the start of the measurement, then there is no reason for this specific event in scientifically comprehensible nature – in contrast to all processes of classical physics. Newton’s apple falls into the grass after a time that can, at least theoretically, be precisely calculated in advance. But quantum things are different. The intuition of the deterministic theory of nature, which had been trained in mechanical processes since the early modern period, no longer applies, or only applies in macrophysics, which forms mean values over many atoms. This is actually even more outrageous than the ruin of the intuitions of the Aristotelian theory of nature brought about by Galileo, Kepler and Newton. After all, classical physics still agreed with Aristotle that everything must have a reason.