New quantum technology combines free electrons and photons

Researchers from Göttingen (Germany) and Lausanne (Switzerland) have succeeded in creating electron-photon pairs in a controlled manner in an electron microscope for the first time. Using a new method, they were able to accurately detect the particles involved. The results of the study expand the toolbox of quantum technology.

Faster computers, eavesdropping communication, better car sensors – quantum technologies have the potential to revolutionize our lives just like the invention of computers or the internet. Experts around the world are trying to implement the results of basic research in quantum technologies. For this purpose, they often need individual particles, such as photons – elementary particles of light – with suitable properties. However, obtaining individual particles is complicated and requires complex methods. In a study recently published in the journal Sciencethe researchers now present a new method that simultaneously generates two individual particles as a pair.

The international team from the Max Planck Göttingen Institute (MPI) for Multidisciplinary Sciences, the University of Göttingen and the Ecole polytechnique fédérale de Lausanne (EPFL) have succeeded in coupling free electrons and single photons in an electron microscope. In the Göttingen experiment, the beam from an electron microscope passes through an integrated optical chip, manufactured by the Swiss team. The chip consists of a fiber optic coupling and a ring-shaped resonator that stores light by keeping the photons moving in a circular path. “When an electron scatters at the initially empty resonator, a photon is generated,” explains Armin Feist, a scientist at MPI and one of the first authors of the study. “In the process, the electron loses exactly the amount of energy the photon needs to be created from virtually nothing in the resonator. As a result, the two particles are coupled through their interaction and form a pair. Using an improved measurement method, physicists were able to accurately detect the individual particles involved and their simultaneous manifestation.

Future quantum technology with free electrons

“With the electron-photon pair, it suffices to measure one particle to obtain information on the energy content and the temporal aspect of the second”, emphasizes Germaine Arend, doctoral student at MPI and also first author of the study. This allows researchers to use one quantum particle in an experiment while confirming its presence by detecting the other particle, in a so-called announcement scheme. Such functionality is necessary for many applications in quantum technology.

Max Planck’s director Claus Ropers sees electron-photon pairs as a new opportunity for quantum research: “The method opens up fascinating new possibilities in electron microscopy. In quantum optics, entangled photon pairs are already improving imaging. can now be explored with electrons. Tobias Kippenberg, professor at EPFL adds: “For the first time, we are introducing free electrons into the toolbox of quantum information science. More broadly, the coupling of free electrons and light using integrated photonics could pave the way for a new class of hybrid quantum technologies. ”

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Materials provided by Max-Planck-Gesellschaft. Note: Content may be edited for style and length.

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