|Fields||Physics, Quantum mechanics|
|Thesis||Neutron depolarization measurements on a Dy-single crystal (1972)|
|Doctoral advisor||Helmut Rauch|
Anton Zeilinger (German: [ˈanton ˈtsaɪlɪŋɐ]; born 20 May 1945) is an Austrian quantum physicist and Nobel laureate in physics of 2022. Zeilinger is professor of physics emeritus at the University of Vienna and senior scientist at the Institute for Quantum Optics and Quantum Information of the Austrian Academy of Sciences. Most of his research concerns the fundamental aspects and applications of quantum entanglement.
In 2007, Zeilinger received the first Inaugural Isaac Newton Medal of the Institute of Physics, London, for "his pioneering conceptual and experimental contributions to the foundations of quantum physics, which have become the cornerstone for the rapidly-evolving field of quantum information". In October 2022, he received the Nobel Prize in Physics, jointly with Alain Aspect and John Clauser for their outstanding work involving experiments with entangled photons, establishing the violation of Bell inequalities and pioneering quantum information science.
Anton Zeilinger was born in 1945 in Ried im Innkreis, Upper Austria, Austria. He studied physics at the University of Vienna from 1963 to 1971. He received a doctorate from the University of Vienna in 1971, with a thesis on "Neutron depolarization measurements on a Dy-single crystal" under Helmut Rauch. He qualified as a university lecturer (habilitation) at the Vienna University of Technology in 1979.
In the 1970s, Zeilinger worked at the Vienna Atominstitut as a research assistant and associate researcher at the Massachusetts Institute of Technology Neutron Diffraction Laboratory until 1979, when he accepted the position of assistant professor at the same Atominstitut. That year he qualified as a university professor. at the Vienna University of Technology.
In 1981 Zeilinger returned to MIT in 1981 as an associate professor on the physics faculty until 1983. Between 1980 and 1990 he worked as a professor at the Vienna University of Technology, the Technical University of Munich, the University of Innsbruck and the University of Vienna. He was also, between 2004 and 2013, the scientific director of the Institute for Quantum Optics and Quantum Information in Vienna between 2004 and 2013. Zeilinger became professor emeritus at the University of Vienna in 2013. He was president of the Austrian Academy of Sciences from 2013 till 2022.
Since 2006, Zeilinger is the vice chairman of the board of trustees of the Institute of Science and Technology Austria, an ambitious project initiated by Zeilinger's proposal. In 2009, he founded the International Academy Traunkirchen, which is dedicated to the support of gifted students in science and technology. He is a fan of the Hitchhiker's Guide To The Galaxy by Douglas Adams, going so far as to name his sailboat 42.
Main article: Quantum teleportation
Most widely known is his first realization of quantum teleportation of an independent qubit. He later expanded this work to developing a source for freely propagating teleported qubits and quantum teleportation over 144 kilometers between two Canary Islands. Quantum teleportation is an essential concept in many quantum information protocols. Besides its role for the transfer of quantum information, it is also considered as an important possible mechanism for building gates within quantum computers.
Main article: Entanglement swapping
Entanglement swapping is the teleportation of an entangled state. After its proposal, entanglement swapping has first been realized experimentally by Zeilinger's group in 1998. It was then applied to carry out a delayed-choice entanglement swapping test.
Anton Zeilinger contributed decisively to the opening up of the field of multi-particle entanglement. In 1990, he was the first with Daniel Greenberger and Michael Horne to work on entanglement of more than two qubits. The resulting GHZ theorem (see Greenberger–Horne–Zeilinger state) is fundamental for quantum physics, as it provides the most succinct contradiction between local realism and the predictions of quantum mechanics.
GHZ states were the first instances of multi-particle entanglement ever investigated.
Finally, in 1999, he succeeded in providing the first experimental evidence of entanglement beyond two particles and also the first test of quantum nonlocality for GHZ states.
In 1998 (published in 2000), his group was the first to implement quantum cryptography with entangled photons.
He then also applied quantum entanglement to optical quantum computation, where in 2005, he performed the first implementation of one-way quantum computation. This is a protocol based on quantum measurement as proposed by Knill, Laflamme and Milburn.
The experiments of Zeilinger and his group on the distribution of entanglement over large distances began with both free-space and fiber-based quantum communication and teleportation between laboratories located on the different sides of the river Danube. This was then extended to larger distances across the city of Vienna and over 144 km between two Canary Islands, resulting in a successful demonstration that quantum communication with satellites is feasible. His dream is to put sources of entangled light onto a satellite in orbit. A first step was achieved during an experiment at the Italian Matera Laser Ranging Observatory.
With his group, Anton Zeilinger made many contributions to the realization of novel entangled states. The source for polarization-entangled photon pairs developed with Paul Kwiat when he was a PostDoc in Zeilinger's group became a workhorse in many laboratories worldwide. The first demonstration of entanglement of orbital angular momentum of photons opened up a new burgeoning field of research in many laboratories.
Zeilinger is also interested to extend quantum mechanics into the macroscopic domain. In the early 1990s, he started experiments in the field of atom optics. He developed a number of ways to coherently manipulate atomic beams, many of which, like the coherent energy shift of an atomic De Broglie wave upon diffraction at a time-modulated light wave, have become cornerstones of today's ultracold atom experiments. In 1999, Zeilinger abandoned atom optics for experiments with very complex and massive macro-molecules – fullerenes. The successful demonstration of quantum interference for these C60 and C70 molecules in 1999 opened up a very active field of research.
In 2005, Zeilinger with his group again started a new field, the quantum physics of mechanical cantilevers. The group was the first – in the year 2006 along with work from Heidmann in Paris and Kippenberg in Garching – to demonstrate experimentally the self-cooling of a micro-mirror by radiation pressure, that is, without feedback.
Using orbital angular momentum states, he was able to demonstrate entanglement of angular momentum up to 300 ħ.
Zeilinger's program of fundamental tests of quantum mechanics is aimed at implementing experimental realizations of many non-classical features of quantum physics for individual systems. In 1998, he provided the final test of Bell's inequality closing the communication loophole by using superfast random number generators. His group also realized the first Bell inequality experiment implementing the freedom-of-choice condition and provided the first realization of a Bell test without the fair sampling assumption for photons.
Among the further fundamental tests he performed the most notable one is his test of a large class of nonlocal realistic theories proposed by Leggett. The group of theories excluded by that experiment can be classified as those which allow reasonable subdivision of ensembles into sub-ensembles. It goes significantly beyond Bell's theorem. While Bell showed that a theory which is both local and realistic is at variance with quantum mechanics, Leggett considered nonlocal realistic theories where the individual photons are assumed to carry polarization. The resulting Leggett inequality was shown to be violated in the experiments of the Zeilinger group.
In an analogous way, his group showed that even quantum systems where entanglement is not possible exhibit non-classical features which cannot be explained by underlying non-contextual probability distributions.
Anton Zeilinger's earliest work is perhaps his least known. His work on neutron interferometry has provided an important foundation for his later research achievements. As a member of the group of his thesis supervisor, Helmut Rauch, at the Technical University of Vienna, Zeilinger participated in a number of neutron interferometry experiments at the Institut Laue–Langevin (ILL) in Grenoble. His very first such experiment confirmed a fundamental prediction of quantum mechanics, the sign change of a spinor phase upon rotation. This was followed by the first experimental realization of coherent spin superposition of matter waves. He continued his work in neutron interferometry at MIT with C.G. Shull (Nobel Laureate), focusing specifically on dynamical diffraction effects of neutrons in perfect crystals which are due to multi-wave coherent superposition. After his return to Europe, he built up an interferometer for very cold neutrons which preceded later similar experiments with atoms. The fundamental experiments there included a most precise test of the linearity of quantum mechanics. Zeilinger built a beautiful double-slit diffraction experiment on the S18 instrument at the Institut Laue-Langevin which, later on, gained in accuracy and could act with only one neutron at a time in the apparatus.
Zeilinger has written more than 550 scientific articles, of which 500 are peer reviewed and 16 are considered highly cited papers.
Zeilinger has been interviewed by Morgan Freeman in season 2 of Through the Wormhole.
Anton Zeilinger was bestowed with the "Großes Bundesverdienstkreuz mit Stern"
Johnjoe McFadden on the physicist who could just make the dream of teleportation possible