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115 | 2016
Annuaire du Collège de France 2014-2015
Résumé des cours et travaux 115e année
VI. Conférenciers invités

Two conferences

Anton Zeilinger
p. 885-886

Editor's notes

Conférences prononcées les 25 mars et 1er avril 2015 (invitation sur proposition du Pr Serge Haroche).

Full text

Quantum imaging and the role of information

1Entangled quantum states provide novel ways for nonlocal imaging. Well known is ghost imaging where the image appears for a photon entangled with the one which interacts with the object. Most recently, it was seen that exploiting just the product state nature of photon pairs, one can obtain imaging where the photon interacting with the object does not even have to be detected.

2In this lecture, I will discuss particularly the role of information in these imaging methods, and it will be shown that in some experiments, the photon interacting with the sample has to be detected in order to destroy path information and make imaging possible. In the more recent case, this is not necessary at all. It turns out that the phenomenon of “quantum imaging with undetected photons” exploits the fact that the phase of a product state cannot be localized. I will present practical applications and an outlook for future experiments.

Quantum entanglement in higher dimensions

3Most fundamental experiments in quantum mechanics have been performed with qubits, i.e. in rather low dimensional Hilbert spaces. Various experimental techniques have recently opened up discrete higher dimensions for experiments. These are particularly multi-mode interference and photon states with more complex wavefronts, like orbital angular momentum (OAM) states.

4In the talk, I will present some recent results focusing on OAM states and on verifications of entanglement in very high dimensions. So far, entanglement of quantum states with quantum numbers around 1,000 and of superposition in more than 100-dimensional Hilbert space have been realized. This may shed interesting light on the question of the quantum-classical transition. I will also discuss recent experiments for using some of these states in quantum communication with higher alphabets.

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Bibliographical reference

Annuaire du Collège de France 2014-2015. Résumé des cours et travaux 115e année, Paris, Collège de France, novembre 2016, p. 885-886. ISBN 978-2-7226-0453-7

Electronic reference

Anton Zeilinger, « Two conferences », L’annuaire du Collège de France [Online], 115 | 2016, Online since 22 June 2018, connection on 03 March 2021. URL : ; DOI :

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About the author

Anton Zeilinger

Professeur, université de Vienne, président de l’Académie autrichienne des sciences (Autriche)

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Collège de France

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