Weirdness and wonder: Quantum entanglement work wins 2022 Nobel Prize for Physics

“This prize is an encouragement to young people — the prize would not be possible without the more than 100 young people who worked with me over the years,” said Anton Zeilinger during a press conference where he was announced as one of the winners of the 2022 Nobel Prize for Physics.

Zeilinger, along with John Clauser and Alain Aspect, have been awarded the prize “for their experiments with entangled photons, establishing the violation of Bell’s inequalities and pioneering quantum information science.” Bell’s inequalities, named after physicist John Stewart Bell, place a limit on the correlations that can be observed in a classical system. Research in quantum mechanics has predicted that particular types of experiments would violate Bell’s inequality, resulting in a stronger correlation.

Working independently, Zeilinger, Clauser, and Aspect did key experiments which measured violations of Bell’s inequality and collectively established the existence of quantum entanglement. In this bizarre phenomenon, two particles, although widely separated, appear to share information even though there is no conceivable way to communicate. The prize-winning results have paved the way for new technologies based on quantum information.

“Today's Nobel Prize in Physics announcement further confirms the fundamental and revolutionary impact the field of optics and has photonics on the progress of science and technology,” said SPIE CEO Kent Rochford. “SPIE congratulates Alain Aspect, John Clauser, and Anton Zeilinger on this well-deserved distinction and recognition of their work. Quantum technologies will increasingly pervade our lives and, as Aspect, Clauser, and Zeilinger join the previous 40-plus optics-related Nobel laureates, we look forward to the exciting future outcomes their research will enable.”

This isn't Star Trek

With his research group, Zeilinger, professor emeritus of physics at the University of Vienna and senior scientist at the Institute for Quantum Optics and Quantum Information of the Austrian Academy of Sciences, demonstrated the phenomenon of quantum teleportation, which makes it possible to move a quantum state from one particle to one at a distance. "Using entanglement, you can transfer all the information which is carried by an object over to some other place where the object is, so to speak, reconstituted," said Zeilinger. He noted that this only works for tiny particles. "It is not like in the Star Trek films transporting something, certainly not the person, over some distance.”

In his work, Clauser, an experimental physicist who researched interferometry and quantum theory, took measurements that supported quantum mechanics by clearly violating a Bell inequality. This showed that quantum mechanics cannot be replaced by a theory that uses hidden variables.

Following the announcement of the prize, Clauser talked about the early days of his experiments in a telephone interview with Adam Smith, chief scientific officer of Nobel Prize Outreach. “While I was doing the experiment [at Columbia], I had a short conversation where Richard Feynman kind of threw me out of his office,” said Clauser. “He was offended that I should even be considering the possibility that quantum mechanics might not give the correct predictions. And only through the very kind efforts of Charlie Townes and Howard Shugart at Cal Berkeley was I able to do the experiments. Afterwards, all my faculty still in Columbia said, Why, what a waste of time! You got the results that everybody expected — now start doing some real physics.’”

Aspect, professor at the Institut d'Optique Graduate School, where he holds the Augustin Fresnel chair, and at École Polytechnique, developed a setup that closed an important loophole in Clauser’s experiment. By switching the measurement settings after an entangled pair had left its source, the setting that existed when they were emitted could not affect the result.

Or, as Smith noted in his after-announcement interview with Aspect, “It’s a very important point. The phenomenon you studied, this quantum entanglement, is so weird.”

Aspect agreed. “Yes. Absolutely, absolutely. And it’s so weird that as I presented in the Nobel symposium a few weeks ago, the fact that I am accepting in my mental images something which is totally crazy, which is nonlocality. Of course, I know that nonlocality does not allow you to send a useful message faster than light, but in my mental images I have accepted nonlocality because otherwise I cannot even think of entanglement, except in the equations of course. But if I want to have an image, I put nonlocality in my image. Nonlocality is the fact that there is a kind of instantaneous relation between two objects, of course something that Einstein could not accept. But he had realized that entanglement meant that.”

"Quantum information science is a vibrant and rapidly developing field," said Eva Olsson, a member of the Nobel committee. "It has broad and potential implications in areas such as secure information transfer, quantum computing, and sensing technology. Its origin can be traced to that of quantum mechanics. Its predictions have opened doors to another world, and it has also shaken the very foundations of how we interpret measurements."

Related SPIE content:

Nobel Prize-winning authors in SPIE Digital Library
To celebrate the winners of the 2022 Nobel Prize for Physics, SPIE is providing their SPIE publications free to the community through the end of 2022. Njut av!

From Einstein doubt to quantum bit: A second quantum revolution
A plenary presentation from SPIE Photonics Europe 2018.

Single and entangled photons: At the heart of the quantum revolutions
A thematic presentation from the International Year of Light opening ceremony in Paris.

Single photons from a satellite: Quantum communication in space
Transferring quantum communication to space poses interesting challenges in both cryptography and fundamental physics.