The 2022 Nobel Prize for Physics was awarded to experimental physicists Alain Aspect, John Clauser, and Anton Zeilinger. The three pioneers conducted groundbreaking research using entangled quantum particles — subatomic particles that behave as if they are linked even when there is nothing between them — a process that Albert Einstein famously called “spooky action at a distance”.
“Quantum information science is a vibrant and rapidly developing field,” said Eva Olsson, a member of the Nobel Committee for Physics. “It has broad potential implications in areas such as secure information transfer, quantum computing, and sensing technology.”
But it wasn’t always like this. In fact, quantum physics itself was a fiercely debated field. In the 1930s, one of the fiercest clashes in physics history erupted between Albert Einstein on one hand and Niels Bohr and Erwin Schrödinger on the other (all three Nobel laureates). Einstein believed that everything had to be concrete and knowledgeable at a fundamental level, whereas the pioneers of quantum mechanics argued that reality can be uncertain and particles don’t possess certain properties until they are measured.
John Clauser initially thought Einstein was right, and in the 1970s, he set out clever experiments to settle the debate. But it didn’t go as planned: in fact, his experiments disproved Einstein and laid the groundwork for a deeper understanding of quantum mechanics — and in particular, quantum entanglement.
Quantum entanglement really is a bizarre process. It’s essentially a phenomenon that can occur when some particles (most commonly photons) are linked together in a way that persists no matter how far apart they are in space and they have a state that cannot be described independently of each other. For instance, physical properties such as position, momentum, spin, and polarization can be perfectly correlated between entangled particles even when they are miles away from each other. Basically, you can study one of the entangled particles and gain information about the linked particles as well — a phenomenon that has no equivalent in classical mechanics.
“I would not call entanglement ‘one,’ but rather ‘the’ trait of quantum mechanics,” Thors Hans Hansson, a member of the Nobel Committee, quoted Schrödinger as writing in 1935. “The experiments performed by Clauser and Aspect opened the eyes of the physics community to the depth of Schrödinger’s statement, and provided tools for creating and manipulating and measuring states of particles that are entangled although they are far away.”
Einstein (and many other physicists) suspected that if the particles are linked, then there must be some ‘hidden variables’ to connect them, or something that would tie them together. Instead, experimental research from the three laureates showed that there is a genuine entanglement that is not owed to other factors.
Celebrating teamwork
Ironically, Clauser, who runs his own company in California now, recalls how his advisor thought this field of research was a “waste of time” and advised him to focus on something else and warned him against “ruining” his career. Well, as it turns out, the very opposite happened.
The trio’s experiments were also previously awarded the Wolf Prize, sometimes considered a precursor to the Nobel Prize. In fact, the three have been considered “favorites” for a Nobel Prize for a decade.
However, Zeilinger, who is currently a professor of physics at the University of Vienna, was very eager to point out that the three did not work alone, and dedicated the prize to the young people who helped in doing the work.
“This prize is an encouragement to young people,” said Zeilinger. “It would not be possible without more than 100 young people who worked with me over the years.”
Zeilinger also gave some advice to young researchers, echoing the thoughts of Dennis Sullivan, the 2022 Abel Prize laureate (in mathematics): “Do what you find interesting, and don’t care too much about possible applications.”
But it should also be said that the trio’s Nobel Prize also considered the applications of their experiments.
Important applications
While the field of quantum mechanics seems ethereal and removed from everyday life, researchers are increasingly finding applications for this technology.
For starters, the quantum computers that have so much promise to solve complex problems are based on quantum processes studied by the three physicists. Another application is quantum communications, a technology with security that promises to be nigh-unbreakable.
For instance, a research group from China managed to beam up entangled pairs of photons to a satellite, proving that entanglement can survive trips of over 1,000 kilometers — that group was spearheaded by one of Zeilinger’s former students. This type of quantum voyage paves the way for securing messages with a “quantum key” that gets destroyed any time someone attempts to eavesdrop and intercept the information. Basically, this could mean essentially unbreakable cryptography.
However, while the field is growing rapidly and it has a lot of potential, there is much we still don’t know about entanglement. In theory, everything could be entangled, but practically, the process seems chaotic and random, and the largest experiments have entangled around a dozen photons. Another project has entangled around a thousand atoms with a single photon.
In 2021, the Nobel Prize for Physics was awarded to three researchers who study complex systems that are particularly important for climate science.
Earlier this week, the Nobel committee awarded the Physiology or Medicine prize to Svante Pääbo for his many contributions “concerning the genomes of extinct hominins and human evolution.” All Nobel Prizes come with a cash reward worth 10 million Swedish krona ($920,000); if there are multiple laureates, the reward is shared.
