Quantum network nodes with warm atoms

Communication networks need nodes at which information is processed or rerouted. Physicists at the University of Basel have now developed a network node for quantum communication networks that can store single photons in a vapor cell and pass them on later.

A particle of light from the single photon source (below) is stored in the vapor cell (above). A simultaneously emitted second photon is revealed by a detector (right), which triggers the control laser pulse and thereby initiates the storage process. (Image: Department of Physics/University of Basel)

In quantum communication networks, information is transmitted by single particles of light (photons). At the nodes of such a network buffer elements are needed which can temporarily store, and later re-emit, the quantum information contained in the photons.

Researchers at the University of Basel in the group of Prof. Philipp Treutlein have now developed a quantum memory that is based on an atomic gas inside a glass cell. The atoms do not have to be specially cooled, which makes the memory easy to produce and versatile, even for satellite applications. Moreover, the researchers have realized a single photon source which allowed them to test the quality and storage time of the quantum memory. Their results were recently published in the scientific journal PRX Quantum.  

Warm atoms in vapor cells
“The suitability of warm atoms in vapor cells for quantum memories has been investigated for the past twenty years”, says Gianni Buser, who worked on the experiment as a PhD student. “Usually, however, attenuated laser beams – and hence classical light – were used”. In classical light, the number of photons hitting the vapor cell in a certain period follows a statistical distribution; on average it is one photon, but sometimes it can be two, three or none.

Original publication
Gianni Buser, Roberto Mottola, Björn Cotting, Janik Wolters, and Philipp Treutlein
Single-Photon Storage in a Ground-State Vapor Cell Quantum Memory
PRX Quantum (2022). doi: 10.1103/PRXQuantum.3.0

Further information
Research group Treutlein