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The 2022 Nobel prize in physics has been jointly awarded to , and for experiments with entangled photons and their work in pioneering quantum information science.

鈥淚鈥檓 still kind of shocked, but it鈥檚 a very positive shock,鈥� said Zeilinger during a press conference.

All three winners were awarded for their fundamental contributions to work on quantum mechanics, which involved experiments using entangled, or connected, particles of light called photons. These showed that information could be instantly transmitted over infinite distances, known as quantum teleportation.

Each of the winners鈥� experiments carried out a real-life test of a mathematical theorem first proposed by physicist John Bell in 1964, called Bell鈥檚 theorem. This attempts to measure whether quantum mechanics is like the billiard-ball model of Newtonian mechanics, where one thing must follow another at a local scale, or whether particles separated by any amount of space can affect each other.

Bell鈥檚 proposal involved measuring the properties of two entangled particles in a system isolated from anything else that could influence the results 鈥� such as an observer inadvertently affecting an entangled partner through measurement 鈥� to see if they exceed a certain value, creating a mathematical inequality and proving that local effects alone can鈥檛 explain quantum mechanics.

In 1972, John F. Clauser and his colleague Stuart J. Freedman were the first to test Bell鈥檚 inequality, by measuring the entangled photons that came from collisions of calcium atoms.

Clauser and Freedman鈥檚 data appeared to violate Bell鈥檚 inequality, the first real-world example to do so, at a high level of statistical accuracy, implying that quantum mechanics really could have non-local effects. However, there were certain loopholes with this experiment, which had many differences from Bell鈥檚 original idea.

In 1980, Alain Aspect at the University of Paris-Saclay, France, and his colleagues managed to measure the Bell inequality again, to a much greater degree of precision and with less doubt, by measuring the polarisation (or orientation) of pairs of photons.

The team used a random switching device to decide which photon to measure before they had reached the detectors. This ruled out the chance of an observer having an effect, as some critics had thought might occur in Clauser鈥檚 experiment, and many physicists felt that Aspect鈥檚 measurements laid to rest the idea that quantum mechanics acted locally.

In 1989, Anton Zeilinger at University of Vienna, Austria, and his colleagues expanded Bell鈥檚 inequality beyond just two entangled particles to a state of three or more entangled particles called a GHZ state. This forms a key pillar for many quantum technologies, including quantum computing, which can use GHZ states to make quantum bits, or qubits.

鈥淲e wanted to go back and honour the people who laid the ground for what was to become [quantum information science],鈥� said Thors Hans Hansson, a member of the Nobel Committee for Physics, during the press conference.

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