Anton Zeilinger

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Anton Zeilinger

The quantum age has been upon us for some time now. Applications in this field are being explored extensively. With his work on quantum cryptography and teleportation, quantum researcher Anton Zeilinger has laid essential foundations for the new world of quantum communication. At the same time, the Nobel Laureate in Physics has intensified the scientific focus on the fundamental building blocks of our universe. His work on quantum entanglement addresses theoretical problems dating back to Albert Einstein.

September 29, 2017, was a special day for quantum research. Scientists and journalists gathered to witness an unprecedented event: a video conference between Vienna and Beijing, encrypted using quantum cryptography. China had launched the satellite Micius into space the year before, enabling quantum-encrypted communication between continents. Micius generated entangled light particles with random oscillation directions, which were sent to ground stations in Xinglong and Graz. With their help, a quantum key was created, making the conversation completely secure from interception or wiretapping. The name of one of the participants in this 2017 video conference is inseparably linked to the research process that allowed it to happen: Anton Zeilinger. The quantum physicist and now Nobel Laureate in Physics was also the President of the Austrian Academy of Sciences (OeAW) in 2017 and spoke with his Chinese counterpart, Chunli Bai, on a quantum-encrypted connection.

In 2017, the satellite Micius was also the main protagonist of another experiment in another field of research that Zeilinger’s work has significantly influenced: quantum teleportation. Jian-Wei Pan, a student of Zeilinger’s, demonstrated that the states of entangled particles could be transmitted hundreds of kilometers through space between the satellite and ground stations. Two ground stations located 1200 kilometers apart were connected through the teleportation of particle states. The previous record had been set by the pioneer himself. In 2012, Zeilinger had transmitted quantum states over 140 kilometers between the islands of La Palma and Tenerife.

These groundbreaking experiments give us a sneak peek at applications that will transform our world. They foreshadow a future characterized by quantum-based networks, computers, and communication infrastructures. At the same time, they make the insights into the astonishing phenomenon of quantum entanglement tangible, insights which have emerged from a multitude of revolutionary scientific ideas and groundbreaking experiments spanning decades. Zeilinger, whose research has been significantly influenced by the support of the Austrian Science Fund (FWF) since 1980, with total funding of several million euros, has played a crucial role in this development.

In a nutshell

Anton Zeilinger is considered a pioneer in the quantum information transfer using photons which is “fundamentally important in the transmission of information in quantum computers”, explains the Nobel Prize laureate.

Anton Zeilinger erhält den Nobelpreis überreicht — It was a historic moment for basic research in Austria when quantum physicist Anton Zeilinger received the Nobel Prize in Physics from Sweden’s King Carl XVI Gustaf. The prestigious award not only honors an exceptional career, but also shows the potential of Austria as a research location, given the right conditions. © ÖAW/Daniel Hinterramskogler

Experiment mit Quanten — Unbounded curiosity: A quantum experiment by Anton Zeilinger at the Institute of Quantum Optics and Quantum Information Vienna of the Austrian Academy of Sciences. © ÖAW/Klaus Pichler

In 1976, more than 40 years before the 2017 video conference, only a handful of scientists were studying quantum entanglement, including renowned physicists like John Bell and Bernard d'Espagnat. One of the first workshops on quantum entanglement took place at that time, during a physics conference in Erice, Sicily. Zeilinger was also present. For him, this event initially sparked his interest in the subject, as he recalled in his Nobel Prize speech at the University of Vienna. “I met all these important people there, and I had no idea what they were talking about. But it was clear that it was fascinating.”

Back then, the discovery of quantum entanglement was only a few decades old. Albert Einstein, who first discussed it in a publication in 1935 together with Boris Podolsky and Nathan Rosen, believed that what he referred to as “spooky action at a distance” contradicted the theory of relativity. Two particles with completely random, predetermined properties always show the same (or, depending on the type of entanglement, opposite) measurement result, even though there is no communication between them – Einstein rejected this idea. He assumed the existence of hidden variables that were yet to be discovered. However, Niels Bohr, who engaged in famous public debates with Einstein, together with Werner Heisenberg, prevailed with their Copenhagen interpretation of quantum physics, in which randomness, probabilistic nature, and uncertain causality are determining elements. The question of whether hidden variables could still exist was not definitively settled. Zeilinger would play an important role in answering this question.

In 1964, John Stewart Bell laid the foundation for refuting Einstein's assumption of hidden variables with his famous Bell’s inequality. This approach was experimentally confirmed first by US physicist John Clauser, and later by his French colleague Alain Aspect. Ultimately, it was Zeilinger, together with Michael Horne and Daniel Greenberger, who definitively confirmed Bell’s theorem – theoretically in 1989 and experimentally ten years later. Their proof came “without inequalities,” as highlighted by the title of their 1989 publication. The GHZ experiment conducted by the three physicists in 1999 – the abbreviation comes from their last names – was able to exclude all theories based on hidden variables with only a few measurements using entangled states of three particles. Einstein was once again proven wrong, but this time even more effectively. Clauser, Aspect, and Zeilinger received the Nobel Prize in Physics in 2022 for their research. All nine of Zeilinger’s original publications recognized by the Nobel Prize Committee were funded by the Austrian Science Fund (FWF).

Numerous new technologies for the creation, manipulation, and measurement of quantum states had to be developed for the GHZ experiment. An important milestone was a 1995 study in which Zeilinger and his colleagues introduced a novel source of entangled photons based on nonlinear crystals. For Zeilinger, the underlying principle of “spontaneous parametric down-conversion” became a “workhorse” for subsequent experiments, as he describes it. However, technologies like these also made experiments in the field of teleportation and cryptography possible. The work on teleportation, in which quantum states can be transmitted from one location to another using an entangled particle pair, was merely a “spin-off of GHZ” for Zeilinger.

A theoretical approach to teleportation was proposed as early as 1993 by a research group led by William Wooters. “When that study came out, we said it was completely impossible to implement experimentally, not knowing that we were already developing the tools for it,” Zeilinger recalled. He successfully conducted the first teleportation experiment in 1997. Shortly thereafter came the first experiment in quantum cryptography, made possible by the techniques of the GHZ experiment. The first image securely transmitted through quantum cryptography at that time depicted the Venus of Willendorf. Essential paradigms for the upcoming quantum age had been established.

Short bio

Anton Zeilinger studied physics and mathematics at the University of Vienna and obtained his doctorate under nuclear physicist Helmut Rauch. In 1979, he received his habilitation at the Vienna University of Technology. After spending time abroad, he joined the faculty of the University of Innsbruck as a professor in 1990. His experiments on quantum teleportation in Innsbruck made him known to a wider audience. In 1999, he accepted a position at the University of Vienna and became the head of the Institute of Experimental Physics and the dean of the Faculty of Physics. He also co-founded and headed the Institute for Quantum Optics and Quantum Information at the Austrian Academy of Sciences in Vienna. From 2013 until mid-2022, Zeilinger served as the President of the Austrian Academy of Sciences. In 2022, he was awarded the Nobel Prize in Physics along with Alain Aspect (France) and John Clauser (USA). The Austrian Science Fund (FWF) has provided funding for many of Zeilinger’s research projects since 1980.

In 2022, the Nobel Committee for Physics noted that laureates Clauser, Aspect, and Zeilinger have paved the way for new technologies based on quantum information. The effects of quantum mechanics are now beginning to manifest in applications. Zeilinger consistently emphasizes that he himself never specifically worked towards this applicability. According to him, researchers should be guided solely by curiosity and pursue their ideas uncompromisingly. “If you're interested in something, then do it and ignore what anyone else says. That's the most important thing,” the Nobel laureate once said in an interview.