Defects in thin molybdenum sulfide layers, generated by bombardment with helium ions, can serve as nano-light sources for quantum technologies.
Defects in thin molybdenum sulfide layers, generated by bombardment with helium ions, can serve as nano-light sources for quantum technologies.
Image: Christoph Hohmann / MCQST
  • Research news
  • Reading time: 3 MIN

Quantum light sources pave the way for optical circuitsLight in the nanoworld

An international team headed up by Alexander Holleitner and Jonathan Finley, physicists at the Technical University of Munich (TUM), has succeeded in placing light sources in atomically thin material layers with an accuracy of just a few nanometers. The new method allows for a multitude of applications in quantum technologies, from quantum sensors and transistors in smartphones through to new encryption technologies for data transmission.

Previous circuits on chips rely on electrons as the information carriers. In the future, photons which transmit information at the speed of light will be able to take on this task in optical circuits. Quantum light sources, which are then connected with quantum fiber optic cables and detectors are needed as basic building blocks for such new chips.

An international team headed up by TUM physicists Alexander Holleitner and Jonathan Finley has now succeeded in creating such quantum light sources in atomically thin material layers and placing them with nanometer accuracy.

First step towards optical quantum computers

“This constitutes a first key step towards optical quantum computers,” says Julian Klein, lead author of the study. “Because for future applications the light sources must be coupled with photon circuits, waveguides for example, in order to make light-based quantum calculations possible.”

The critical point here is the exact and precisely controllable placement of the light sources. It is possible to create quantum light sources in conventional three-dimensional materials such as diamond or silicon, but they cannot be precisely placed in these materials.

Deterministic defects

The physicists then used a layer of the semiconductor molybdenum disulfide (MoS2) as the starting material, just three atoms thick. They irradiated this with a helium ion beam which they focused on a surface area of less than one nanometer.

In order to generate optically active defects, the desired quantum light sources, molybdenum or sulfur atoms are precisely hammered out of the layer. The imperfections are traps for so-called excitons, electron-hole pairs, which then emit the desired photons.

Technically, the new helium ion microscope at the Walter Schottky Institute’s Center for Nanotechnology and Nanomaterials, which can be used to irradiate such material with an unparalleled lateral resolution, was of central importance for this.

On the road to new light sources

Together with theorists at TUM, the Max Planck Society, and the University of Bremen, the team developed a model which also describes the energy states observed at the imperfections in theory.

In the future, the researchers also want to create more complex light source patterns, in lateral two-dimensional lattice structures for example, in order to thus also research multi-exciton phenomena or exotic material properties.

This is the experimental gateway to a world which has long only been described in theory within the context of the so-called Bose-Hubbard model which seeks to account for complex processes in solids.

Quantum sensors, transistors and secure encryption

And there may be progress not only in theory, but also with regard to possible technological developments. Since the light sources always have the same underlying defect in the material, they are theoretically indistinguishable. This allows for applications which are based on the quantum-mechanical principle of entanglement.

“It is possible to integrate our quantum light sources very elegantly into photon circuits,” says Klein. “Owing to the high sensitivity, for example, it is possible to build quantum sensors for smartphones and develop extremely secure encryption technologies for data transmission.”


Site-selectively generated photon emitters in monolayer MoS2 via local helium ion irradiation
J. Klein, M. Lorke, M. Florian, F. Sigger, L. Sigl, S. Rey, J. Wierzbowski, J. Cerne, K. Müller, E. Mitterreiter, P. Zimmermann, T. Taniguchi, K. Watanabe , U. Wurstbauer, M. Kaniber, M. Knap, R. Schmidt, J.J. Finley & A.W. Holleitner
Nature Communications, 10, 2755 (2019) – DOI: 10.1038/s41467-019-10632-z

More information:

The work was supported by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation), by the TUM International Graduate School of Science and Engineering (IGSSE), by the clusters of excellence “Nanosystems Initiative Munich” (NIM), “Munich Center for Quantum Science and Technology” (MCQST) and “e-conversion”, the TUM Institute for Advanced Study, the ExQM doctoral program of the Bavarian Elite Network, by the European Union in the context of Horizon 2020, the Photonics Research Germany funding program, and the Bavarian Academy of Sciences and Humanities.

Alongside scientists from the Technical University of Munich, researchers of the Max Planck Institute for Quantum Optics (Garching), the University of Bremen, The State University of New York (Buffalo, USA) and the National Institute for Materials Science (Tsukuba, Japan) were also involved.

High resolution image

Corporate Communications Center

Technical University of Munich Dr. Andreas Battenberg

Contacts to this article:

Prof. Dr. Alexander W. Holleitner
Walter Schottky Institute and Department of Physics
Zentrum für Nanotechnologie und Nanomaterialien
Technical University of Munich
Am Coulombwall 4a, 85748 Garching, Germany
Tel.: +49 89 289 11575

Prof. Dr. Jonathan J. Finley
Walter Schottky Institute and Department of Physics
Technical University of Munich
Am Coulombwall 4, 85748 Garching, Germany
Tel.: +49 89 289 12770

Article at

Nanowires made of germanium-silicon alloy with hexagonal crystal lattice can generate light. They could be integrated directly into the common processes of silicon-based semiconductor technology to produce photonic chips.

A new lightsource for the chip industry

For the past 50 years, researchers around the globe have been looking for a way to make lasers with silicon or germanium. A team from the Technical University of Eindhoven (TU/e) and the Technical University of Munich (TUM)...

Einige Femtosekunden lange Pulse des Pump-Lasers (links) erzeugen elektrische on-chip Pulse im Terahertz-Frequenzbereich. Mit dem rechten Laser wird die Information wieder ausgelesen. (Bild: Christoph Hohmann / NIM, Holleitner / TUM)

Closing the gap: On the road to terahertz electronics

A team headed by the TUM physicists Alexander Holleitner and Reinhard Kienberger has succeeded for the first time in generating ultrashort electric pulses on a chip using metal antennas only a few nanometers in size, then...

Zukunftsvision: Quantencomputer mit Chips aus Diamant und Graphen – Grafik: Christoph Hohmann / NIM

Center for Quantum Engineering comes to Garching

In recent years, a globally esteemed research focus on quantum technologies has developed on the Garching campus. The German Council of Science and Humanities now supports the creation of a new central institute at the...

Benedikt Mayer und Lisa Janker an der Epitaxieanlage im Walter Schottky Institut der TU München – Foto: Uli Benz / TUM

Nanolaser for information technology

Physicists at the Technical University of Munich (TUM) have developed a nanolaser, a thousand times thinner than a human hair. Thanks to an ingenious process, the nanowire lasers grow right on a silicon chip, making it...

Elektron im Quanten-Punkt, beeinflusst von Kernspins der Umgebung – Grafik: Fabian Flassig / TUM

Quantum computer made of standard semiconductor materials

Physicists at the Technical University of Munich, the Los Alamos National Laboratory and Stanford University (USA) have tracked down semiconductor nanostructure mechanisms that can result in the loss of stored information –...

Wismut-Selenid-Probe zwischen zwei Gold-Elektroden – Bild: Christoph Hohmann / NIM

Fascinating quantum transport on a surface

Topological insulators are an exceptional group of materials. Their interior acts as an insulator, but the surface conducts electricity extremely well. Scientists at The Technische Universität München now could measure this...

Zukunftsvision Quantencomputer mit Chips aus Diamant und Graphen – Grafik: Christoph Hohmann / NIM

Possible read head for quantum computers

Nitrogen-vacancy centers in diamonds could be used to construct vital components for quantum computers. But hitherto it has been impossible to read optically written information from such systems electronically. Using a...