Anton Zeilinger From Wikipedia, the free encyclopedia

Anton Zeilinger
A. Zeilinger (cropped).jpg
Born20 May 1945 (age 77)
Ried im Innkreis, Austria
NationalityAustrian
Known forQuantum teleportation
Bell test experiments
Elitzur–Vaidman bomb tester experiment
Greenberger–Horne–Zeilinger state
GHZ experiment
Superdense coding
AwardsKlopsteg Memorial Award (2004)
Isaac Newton Medal (2007)
Wolf Prize in Physics (2010)
Nobel Prize in Physics (2022)
Scientific career
FieldsPhysics, Quantum mechanics
InstitutionsUniversity of Vienna
Technical University of Munich
Technical University of Vienna
Massachusetts Institute of Technology
Collège de France
Merton College, Oxford
Doctoral advisorHelmut Rauch
Doctoral studentsStefanie Barz[1][2]
Pan Jianwei[3]
Thomas Jennewein[4]

Anton Zeilinger (German: [ˈtsaɪlɪŋɐ]; born 20 May 1945) is an Austrian quantum physicist who in 2022 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. In 2008, he received the Inaugural Isaac Newton Medal of the Institute of Physics (UK) 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". Zeilinger is professor of physics at the University of Vienna and Senior Scientist at the Institute for Quantum Optics and Quantum Information IQOQI at the Austrian Academy of Sciences. Most of his research concerns the fundamental aspects and applications of quantum entanglement.

Biography[edit]

Anton Zeilinger, born 1945 in Austria, has held positions at the Technical University of Vienna and the University of Innsbruck. He has held visiting positions at the Massachusetts Institute of Technology (MIT), at Humboldt University in Berlin, Merton College, Oxford and the Collège de France (Chaire Internationale) in Paris. Zeilinger's awards include the Wolf Prize in Physics (2010), the Inaugural Isaac Newton Medal of the IOP (2007) and the King Faisal International Prize (2005). He is a member of seven Scientific Academies. Anton Zeilinger is currently Professor of Physics at the University of Vienna and Senior Scientist at the Institute for Quantum Optics and Quantum Information of the Austrian Academy of Sciences to whose Presidency he was recently elected.[5] 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[6] 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.[7]

Work[edit]

Zeilinger works in the foundations of quantum mechanics. He discovered, together with Daniel Greenberger and Michael Horne, novel counter-intuitive features of three- and four-particle states. He was the first, with his team, to realize those in experiment. This opened the field of multi-particle interference and multi-particle quantum correlations. Using the methods developed there, he performed the first quantum teleportation of an independent qubit. This was followed by the realization of entanglement swapping, a most interesting concept where an entangled state is teleported.[citation needed]

This work was followed by numerous tests of Bell’s inequalities, including a Cosmic Bell Test. Other fundamental experiments concerned Leggett’s nonlocal realistic theories, tests of quantum contextuality in Kochen-Specker experiments, and experiments on nonlocal Schrödinger steering with entangled states.[citation needed]

Many of these results became relevant in the development of quantum information technology, where he also performed pioneering experiments. His experiment on quantum dense coding was the first using entanglement to demonstrate a primitive, not possible in classical physics. He also realized the first entanglement-based quantum cryptography experiment and later, quantum communication over increasing distances and, implementing higher-dimensional states, with increasing information capacity. Possible applications also include one-way quantum computation and blind quantum computation. Among his further contributions to the experimental and conceptual foundations of quantum mechanics are matter wave interference all the way from neutrons via atoms to macromolecules such as fullerenes.[citation needed]

Quantum teleportation[edit]

Most widely known is his first realization of quantum teleportation of an independent qubit.[8] He later expanded this work to developing a source for freely propagating teleported qubits [9] and quantum teleportation over 144 kilometers between two Canary Islands.[10] 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.[citation needed]

Entanglement swapping – teleportation of entanglement[edit]

Main article: Entanglement swapping

Entanglement swapping is the teleportation of an entangled state. After its proposal,[11] entanglement swapping has first been realized experimentally by Zeilinger's group in 1998.[12] It was then applied to carry out a delayed-choice entanglement swapping test.[13] Entanglement swapping is the crucial ingredient for quantum repeaters which are expected to connect future quantum computers.[citation needed]

Entanglement beyond two qubits – GHZ-states and their realizations[edit]

Anton Zeilinger holding a sculpture by Julian Voss-Andreae, photo by J. Godany

Anton Zeilinger contributed decisively to the opening up of the field of multi-particle entanglement.[14] In 1990, he was the first with Daniel Greenberger and Michael Horne to work on entanglement of more than two qubits.[15] The resulting GHZ theorem[16] (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.[citation needed]

GHZ states were the first instances of multi-particle entanglement ever investigated.[17] Surprisingly, multi-particle entangled states exhibit qualitatively different properties compared to two-particle entanglement. In the 1990s, it became the main goal of Zeilinger's research to realize such GHZ states in the laboratory, which required the development of many new methods and tools.[citation needed]

Finally, in 1999, he succeeded in providing the first experimental evidence of entanglement beyond two particles[18] and also the first test of quantum nonlocality for GHZ states.[19] He also was the first to realize that there are different classes of higher-dimensional entangled states and proposed W-states. Today, multi-particle states have become an essential workhorse in quantum computation and thus, GHZ-states have even become an individual entry in the PACS code.[citation needed]

Quantum communication, quantum cryptography, quantum computation[edit]

In 1996, Anton Zeilinger with his group realized hyper-dense coding.[20] There, one can encode into one qubit more than one classical bit of information. This was the first realization of a quantum information protocol with an entangled state, where one is able to achieve something impossible with classical physics.[citation needed]

In 1998 (published in 2000),[21] his group was the first to implement quantum cryptography with entangled photons. Zeilinger's group is now also developing a quantum cryptography prototype in collaboration with industry.[citation needed]

He then also applied quantum entanglement to optical quantum computation, where in 2005,[22] 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.[23] Most recently, it has been shown[24] that one-way quantum computation can be used to implement blind quantum computing. This solves a problem in Cloud computing, namely that, whatever algorithm a client employs on a quantum server is completely unknown, i.e. blind, to the operator of the server.[citation needed]

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.[25] This was then extended to larger distances across the city of Vienna[26] 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.[7] A first step was achieved during an experiment at the Italian Matera Laser Ranging Observatory.[27]

Further novel entangled states[edit]

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[28] became a workhorse in many laboratories worldwide. The first demonstration of entanglement of orbital angular momentum of photons[29] opened up a new burgeoning field of research in many laboratories.[citation needed]

Macroscopic quantum superposition[edit]

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[30] in 1999 opened up a very active field of research. Key results include the most precise quantitative study to date of decoherence by thermal radiation and by atomic collisions and the first quantum interference of complex biological macro-molecules. This work is continued by Markus Arndt [de].[citation needed]

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.[31] That phenomenon can be seen as a consequence of the coupling of a high-entropy mechanical system with a low-entropy radiation field. This work is now continued independently by Markus Aspelmeyer.[citation needed]

Using orbital angular momentum states, he was able to demonstrate entanglement of angular momentum up to 300 ħ.[32]

Further fundamental tests[edit]

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,[33] 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[34] and provided the first realization of a Bell test without the fair sampling assumption for photons.[35] All these experiments are not only of fundamental interest, but also important for quantum cryptography. In 2015, at the same time as the group of Ronald Hanson at Delft University of Technology and the group of Sae-Woo Nam at the National Institute of Standards and Technology (NIST), Zeilinger’s group closed the locality and detection loopholes in Bell experiments,[36] thereby corroborating quantum mechanics and ruling out theories that satisfy local causality and providing definitive proof that quantum cryptography can be unconditionally secure.[citation needed]

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.[37] 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.[38]

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.[39] It is expected that these latter experiments will also open up novel ways for quantum information.[citation needed]

Neutron interferometry[edit]

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.[40] 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 and a beautiful double-slit diffraction experiment with only one neutron at a time in the apparatus. Actually, in that experiment, while one neutron was registered, the next neutron still resided in its Uranium nucleus waiting for fission to happen.[citation needed]

Then, as a professor at the University of Innsbruck, Zeilinger started experiments on entangled photons, as the low phase space density of neutrons produced by reactors precluded their use in such experiments. In all his career, from TU Vienna through Innsbruck and back to the University of Vienna, Zeilinger has had a most salubrious effect on the work of his colleagues and competitors alike, always noting connections and extensions to be investigated and unstintingly sharing remarks that have enhanced the field of quantum mechanics from foundational to purely applied work.[citation needed]

Honours and awards[edit]

International prizes and awards[edit]

Austrian prizes and awards[edit]

Further distinctions[edit]

Distinguished lectureships[edit]

In popular culture[edit]

Zeilinger has been interviewed by Morgan Freeman in season 2 of Through the Wormhole.

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