Generation of entanglement using a short-wavelength seeded free-electron laser

Saikat Nandi, Axel Stenquist, Asimina Papoulia, Edvin Olofsson, Laura Badano, Mattias Bertolino, David Busto, Carlo Callegari, Stefanos Carlström, Miltcho B Danailov, Philipp V Demekhin, Michele Di Fraia, Per Eng-Johnsson, Raimund Feifel, Guillaume Gallician, Luca Giannessi, Mathieu Gisselbrecht, Michele Manfredda, Michael Meyer, Catalin MironJasper Peschel, Oksana Plekan, Kevin C Prince, Richard J Squibb, Marco Zangrando, Felipe Zapata Abellan, Shiyang Zhong, Jan Marcus Dahlström

Research output: Contribution to journalArticlepeer-review


Quantum entanglement between the degrees of freedom encountered in the classical world is challenging to observe due to the surrounding environment. To elucidate this issue, we investigate the entanglement generated over ultrafast timescales in a bipartite quantum system comprising two massive particles: a free-moving photoelectron, which expands to a mesoscopic length scale, and a light-dressed atomic ion, which represents a hybrid state of light and matter. Although the photoelectron spectra are measured classically, the entanglement allows us to reveal information about the dressed-state dynamics of the ion and the femtosecond extreme ultraviolet pulses delivered by a seeded free-electron laser. The observed generation of entanglement is interpreted using the time-dependent von Neumann entropy. Our results unveil the potential for using short-wavelength coherent light pulses from free-electron lasers to generate entangled photoelectron and ion systems for studying spooky action at a distance.

Original languageEnglish
Pages (from-to)eado0668
JournalScience Advances
Issue number16
Publication statusPublished - 2024 Apr 19

Subject classification (UKÄ)

  • Atom and Molecular Physics and Optics


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