Nobel Prize in Physics for key advances in quantum mechanics

The Swedish Royal Academy of Sciences has awarded the Nobel Prize in Physics to the Frenchman Alain Aspect, the American John F. Clauser and the Austrian Anton Zeilinger, for their pioneering experiments in quantum physics.

The members of the committee highlighted that the winners have carried out pioneering experiments on quantum entanglement. “We can see that the work of the laureates on quantum entangled states is of great importance, even beyond fundamental questions about the interpretation of quantum mechanics,” said Anders Irbäck, chairman of the Nobel Committee for Physics.

“The contribution of these three scientists is extremely important, because, through various experiments, they were able to show that two particles behave as a single unit even when they are separated. That is to say, a state where the properties are defined from a whole and not as the sum of the parts”, highlights, in dialogue with the CTyS-UNLaM Agency, Augusto Roncaglia, CONICET researcher with work headquarters in the Department of Physics (Faculty of Exact and Natural Sciences, University of Buenos Aires).

Roncaglia explains that, from their experiments, the three scientists laid solid foundations to validate the quantum theory. “They corroborated all these properties, which are extremely surprising, and paved the way for quantum investigations, which have various applications. One of them, for example, is the secure transmission of information, what is known as quantum cryptography and which is already being applied, from startups that offer this technology to tests of transmission between satellites”, illustrates the researcher.

Anton Zeilinger, one of three quantum physicists who share this year’s Nobel Prize in Physics. (Photo: Jacqueline Godany)

Quantum mechanics is very strange and defies common logic.

Sixty years ago, John Bell developed the theory of a mathematical inequality, which states that if these hidden variables exist, the correlation between the results of a large number of measurements will never exceed a certain value. However, quantum mechanics predicts that if the experiment is performed with certain entangled states, the results of the experiment will give a violation of Bell’s inequality.

“These entangled states can be generated with photons in the laboratory. What the three Nobel Prize-winning scientists did was experimentally verify this prediction – details the CONICET researcher-. Clauser, for example, generated quantum-entangled pairs of photons, and made property measurements on each member of the pair at stations a few meters apart, verifying that quantum mechanics violated Bell’s inequalities.”

Ten years later, Aspect would improve the generation of photons and would also be able to choose the properties to be measured at each station in a pseudo-random way, another of the requirements of Bell’s theorem. “We must bear in mind that the experiment involves a statistical factor, of repeating the emission of photons many times and randomly choosing which direction of polarization to measure while the particles travel at the speed of light. It is an extremely complex scenario”, explains Roncaglia.

Zeilinger, for his part, contributed to the theory of quantum entanglement by verifying these violations of Bell’s inequalities not from meters, but from kilometers away. That is, particles behaving as a unit despite being separated by thousands of kilometers, opening the door to the first quantum teleportation experiments and the transmission of quantum information. “In Argentina, experiments are already being carried out using photons in the Optics and Photonics Laboratory at the Faculty of Exact and Natural Sciences of the University of Buenos Aires and in the Quantum Optics Division of DEILAP-CITEDEF. In other words, we are working on different projects on quantum cryptography”, concludes the expert. (Source: Nicolás Camargo Lescano (CTyS-UNLaM Agency))