Tof his year The Nobel Prize in physics has been awarded to a trio of scientists whose insights into the fundamental principles of quantum mechanics laid the foundations for a new era of technology. Quantum computers, quantum networks and secure quantum cryptography all have their roots in experiments carried out, over several decades, by Alain Aspect, John Clauser and Anton Zeilinger.
Their work revolves around a phenomenon called quantum entanglement, in which two or more particles are correlated with each other so that they behave as if they were individual units. This leads to opposite effects – changing the properties of one particle in a entangled pair, for example, will immediately change the other, no matter how far apart the particles are. They could be next to each other or at opposite ends of the galaxy. Albert Einstein—who was not a fan of the probabilistic nature of quantum mechanics—described entanglement as “spooky action at a distance.” He and others worried that it appeared to violate the rules of special relativity, which stated that nothing could travel faster than the speed of light. If the entangled particles were separated by a great distance, how could information travel between them apparently instantaneously?
In 1935, Einstein and two colleagues, Boris Podolsky and Nathan Rosen, proposed a thought experiment (then known as “EPR paradox”) to investigate whether the strange behavior observed in entanglement implied that quantum mechanics was not a complete description of reality. Perhaps the particles carried with them hidden information, not described by quantum mechanics, about how they might behave during experiments or when measured. In 1964 John Stewart Bell, a physicist at CERNin Geneva, developed it EPR paradox further and came up with testable predictions to determine whether the “hidden variables” actually existed or not.
Almost a decade later, John Clauser constructed the first experiment to test Bell’s idea, and his results agreed with the predictions of quantum mechanics and showed that Einstein’s hidden variables probably did not exist. However, the experiments left some gaps, which were filled in the early 1980s by Alain Aspect, then a graduate student at the University of Paris-Sud in Orsay, France. By adjusting and improving Dr Clauser’s experiments, Dr Aspect put the final nail in the coffin of Einstein’s hidden variables.
The third laureate, Anton Zeilinger of the University of Vienna, has spent decades looking for ways to use quantum entanglement. In 1997 he showed that it was possible to transfer information between particles, a process called “quantum teleportation”. He also showed that two pairs of entangled particles can interact in interesting ways – bring one particle from each entangled pair together and the two remaining particles (which have never been in contact) will become entangled in their sheath.
Manipulating the quantum states of systems of entangled particles has become the basis of technologies such as quantum computing and quantum encryption. Based on the work of this year’s physics laureates, signals consisting of entangled photons (particles of light) have been sent through optical fibers several kilometers long and even transmitted between the ground and a satellite orbiting hundreds of kilometers above Earth.
“Quantum information science is a vibrant and rapidly developing field, with broad and potential implications for areas such as secure information transfer, quantum computing and sensing technology,” said Eva Olsson, a member of the Royal Academy’s physics prize committee. of Sweden. of the science. “His predictions have opened doors to another world.”
Speaking after the announcement, Dr. Zeilinger said he was surprised to receive the call from the academy an hour earlier. “I’m still kind of shocked,” he said, “but it’s a very positive shock.” ■