De Broglie wavelength of a non-local four-photon state

Author(s)
Philip Walther, Jian-Wei Pan, Markus Aspelmeyer, Rupert Ursin, Sara Gasparoni, Anton Zeilinger
Abstract

Superposition is one of the most distinctive features of quantum theory and has been demonstrated in numerous single-particle interference experiments. Quantum entanglement, the coherent superposition of states in multi-particle systems, yields more complex phenomena. One important type of multi-particle experiment uses path-entangled number states, which exhibit pure higher-order interference and the potential for applications in metrology and imaging; these include quantum interferometry and spectroscopy with phase sensitivity at the Heisenberg limit, or quantum lithography beyond the classical diffraction limit. It has been generally understood that in optical implementations of such schemes, lower-order interference effects always decrease the overall performance at higher particle numbers. Such experiments have therefore been limited to two photons. Here we overcome this limitation, demonstrating a four-photon interferometer based on linear optics. We observe interference fringes with a periodicity of one-quarter of the single-photon wavelength, confirming the presence of a four-particle mode-entangled state. We anticipate that this scheme should be extendable to arbitrary photon numbers, holding promise for realizable applications with entanglement-enhanced performance.

Organisation(s)
Quantum Optics, Quantum Nanophysics and Quantum Information
External organisation(s)
Ruprecht-Karls-Universität Heidelberg
Journal
Nature
Volume
429
Pages
158-161
No. of pages
4
ISSN
0028-0836
DOI
https://doi.org/10.1038/nature02552
Publication date
05-2004
Peer reviewed
Yes
Austrian Fields of Science 2012
103026 Quantum optics
Keywords
Portal url
https://ucris.univie.ac.at/portal/en/publications/de-broglie-wavelength-of-a-nonlocal-fourphoton-state(e39a77fb-50b6-4e75-adf8-820d77f31f07).html