## A Win For Quantum Mechanics

Posted by on Tuesday, October 4, 2022

The 2022 Nobel Prize for Physics was announced today, and it is a well deserved win for the quantum mechanics community.

The three recipients this year are Alain Aspect, John Clauser, and Anton Zeilinger for their work on the fundamentals of quantum mechanics, and in particular on quantum entanglement. The research that they conducted in the 1970s and 1980s forms the basis of many of the emerging technologies in quantum computing and quantum communication, and will become increasingly important to the world with the next generation of computers and networks.

As with most of quantum mechanics, the theories that their research is based on are difficult to understand, because they are quite different from what we observed in our everyday world. At the beginning of the twentieth century, physicists had a problem in that the spectrum of light from a heated object did not match the experimental observations. The solution that was eventually found was that light must exist only in discrete packets, called photons. Over the next thirty years, the effects of having discrete packets of energy were further developed by the theoretical physics community, including the phenomena of quantum entanglement.

When two photons are produced together, classical physics predicted that they would then separate and be completely independent of each other. Manipulating one would have no effect on the other. However quantum mechanics made a different and more interesting prediction. According to quantum mechanics, the two photons would continue to be linked together through some unknown mechanism, and by interacting with one of the two photons, the properties of the other one would be altered.

For several decades this was purely theoretical, which no basis in experiment. Then John Clauser developed an experiment that would allow researchers to essentially create pairs of entangled photons, alter the properties of one of the pair, and then measure the properties of the other one. Although it was not possible to measure a single photon well enough to prove the existing of quantum entanglement, but measuring large numbers of photon pairs they were able to show that statistically they were obeying the predictions of quantum mechanics rather than classical physics. Alain Aspect would then refine the experiments, close up several possible loopholes in the interpretation of the results, and finally prove experimentally that quantum entanglement was real.

Anton Zeilinger then used these results to demonstrate a related phenomenon known as quantum teleportation. Since a pair of entangled photons were now known to be able to affect each other, with changes and measurements of one causing the other to change its properties, it was theoretically possible to store information in one set of photons, and have their entangled partners store the same information automatically at some distant location. Unfortunately quantum mechanics deals in probabilities rather than definite states and information, so this information could not be written or read out directly, but rather needed complicated experimental methods. Eventually Zeilinger and his team solved these problems, and were able to instantly "teleport" information from one laboratory to the another without the two systems being able to communicated. It isn't at the level of Star Trek, with entire people being teleported, but it was still revolutionary to have information suddenly move between distant locations. This was the first proof of quantum teleportation.

A full review of the applications of quantum entanglement and quantum teleportation is beyond the scope of this article, but they are fundamental to the next generation of quantum computers and encrypted communications. These methods resulted in new technologies and algorithms that could send a signal between two points in a way that could not be intercepted by a third party, and which could definitively prove to the sender and recipient if someone had tried. Entanglement has also been used as the basis for many quantum computing algorithms which are now being developed in the first quantum computers to perform calculations many orders of magnitude faster than a traditional computer is capable of.

In effect, these three physicists were among the fathers of quantum computing and quantum information. Their work forms the foundation of the next generation of technological innovations, and of the creation of new algorithms and communication methods that we can only dream of.

They are truly worth of the 2022 Nobel Prize in Physics.

The three recipients this year are Alain Aspect, John Clauser, and Anton Zeilinger for their work on the fundamentals of quantum mechanics, and in particular on quantum entanglement. The research that they conducted in the 1970s and 1980s forms the basis of many of the emerging technologies in quantum computing and quantum communication, and will become increasingly important to the world with the next generation of computers and networks.

As with most of quantum mechanics, the theories that their research is based on are difficult to understand, because they are quite different from what we observed in our everyday world. At the beginning of the twentieth century, physicists had a problem in that the spectrum of light from a heated object did not match the experimental observations. The solution that was eventually found was that light must exist only in discrete packets, called photons. Over the next thirty years, the effects of having discrete packets of energy were further developed by the theoretical physics community, including the phenomena of quantum entanglement.

When two photons are produced together, classical physics predicted that they would then separate and be completely independent of each other. Manipulating one would have no effect on the other. However quantum mechanics made a different and more interesting prediction. According to quantum mechanics, the two photons would continue to be linked together through some unknown mechanism, and by interacting with one of the two photons, the properties of the other one would be altered.

For several decades this was purely theoretical, which no basis in experiment. Then John Clauser developed an experiment that would allow researchers to essentially create pairs of entangled photons, alter the properties of one of the pair, and then measure the properties of the other one. Although it was not possible to measure a single photon well enough to prove the existing of quantum entanglement, but measuring large numbers of photon pairs they were able to show that statistically they were obeying the predictions of quantum mechanics rather than classical physics. Alain Aspect would then refine the experiments, close up several possible loopholes in the interpretation of the results, and finally prove experimentally that quantum entanglement was real.

Anton Zeilinger then used these results to demonstrate a related phenomenon known as quantum teleportation. Since a pair of entangled photons were now known to be able to affect each other, with changes and measurements of one causing the other to change its properties, it was theoretically possible to store information in one set of photons, and have their entangled partners store the same information automatically at some distant location. Unfortunately quantum mechanics deals in probabilities rather than definite states and information, so this information could not be written or read out directly, but rather needed complicated experimental methods. Eventually Zeilinger and his team solved these problems, and were able to instantly "teleport" information from one laboratory to the another without the two systems being able to communicated. It isn't at the level of Star Trek, with entire people being teleported, but it was still revolutionary to have information suddenly move between distant locations. This was the first proof of quantum teleportation.

A full review of the applications of quantum entanglement and quantum teleportation is beyond the scope of this article, but they are fundamental to the next generation of quantum computers and encrypted communications. These methods resulted in new technologies and algorithms that could send a signal between two points in a way that could not be intercepted by a third party, and which could definitively prove to the sender and recipient if someone had tried. Entanglement has also been used as the basis for many quantum computing algorithms which are now being developed in the first quantum computers to perform calculations many orders of magnitude faster than a traditional computer is capable of.

In effect, these three physicists were among the fathers of quantum computing and quantum information. Their work forms the foundation of the next generation of technological innovations, and of the creation of new algorithms and communication methods that we can only dream of.

They are truly worth of the 2022 Nobel Prize in Physics.