News archive


June: Interview on quantum repeater research

As of June 2020, Prof. Dr. Christoph Becher, Fachrichtung Physik, Saarland University, was elected speaker of the research network Q.Link.X working on the realization of quantum repeater concepts. Here is an interview on his "visions and missions" for this research (in German).

January: Atomic telecom-photon entanglement over 20 km fibre

Our quantum frequency converter enabled an exciting experiment at LMU Munich on entanglement of internal states of a single trapped atom and a telecom photon over 20 km fiber. The original paper appeared in Physical Review Letters on January, 10, 2020: Tim van Leent, Matthias Bock, Robert Garthoff, Kai Redeker, Wei Zhang, Tobias Bauer, Wenjamin Rosenfeld, Christoph Becher, and Harald Weinfurter, Long-Distance Distribution of Atom-Photon Entanglement at Telecom Wavelength, Phys. Rev. Lett. 124, 010510 (2020).
Press release (in German).
Report on Science Daily (in English)



July: TOP 50 Paper at Nature Communications

Our paper M. Bock et al., "High-fidelity entanglement between a trapped ion and a telecom photon via quantum frequency conversion" was one of the most read TOP50 Nature Communications physics articles in 2018.



March: Johannes Görlitz receives award at 693. WE-Heraeus-Seminar

At the 693. WE-Heraeus-Seminar on Diamond Quantum Technologies (March 25. - 28., Physics Centre, Bad Honnef, Germany), Johannes Görlitz was awarded one of the three best poster awards (Spectroscopic investigation of the neutral charge state of the tin-vacancy centre in diamond). Congratulations!

February: Demonstration of coherent control and four wave mixing in ensembles of SiV centers in diamond

We have demonstrated coherent control, coherent population transfer and four wave mixing resulting in efficient Raman gain and absorption in a very thin (300 nm) diamond sample with an ensemble of SiV centers. The strong light matter interaction explored here will in future enable e.g. Raman-based optical quantum memories and single photon non- linearities such as single photon switches.

The original paper appeared in Physical Review Letters on February, 12, 2019.

Christian Weinzetl, Johannes Görlitz, Jonas Nils Becker, Ian A. Walmsley, Eilon Poem, Joshua Nunn, and Christoph Becher, Coherent Control and Wave Mixing in an Ensemble of Silicon-Vacancy Centers in Diamond

Phys. Rev. Lett. 122, 063601 (2019)



October: Interference of photons from remote sources

Many scientists are working on demonstrably secure communication based on quantum physics – the so-called quantum communication. Current approaches for long-distance signal transmission rely on repeaters which are based on a crucial effect, the interference of two photons, that is, two individual light quanta coming from distant sources. Physicists from University of Stuttgart and Saarland University, in Germany, were now able to manipulate the single photons by means of optically nonlinear crystals without compromising their quantum mechanical nature. This manipulation is necessary to transmit the signal via optical fibers which may enable a large-area quantum network. The results were now published in Nature Nanotechnology.

The original paper appeared in Nature Nanotechnology on October 22, 2018: Jonas H. Weber, Benjamin Kambs, Jan Kettler, Simon Kern, Julian Maisch, Hüseyin Vural, Michael Jetter, Simone L. Portalupi, Christoph Becher & Peter Michler, Two-photon interference in the telecom C-band after frequency conversion of photons from remote quantum emitters, Nature Nanotechnology (2018).

Here is the common press release of Stuttgart and Saarland Universities.


May: Ion-telecom-photon entanglement via quantum frequency conversion

Physicists at Saarland University in Saarbrücken, Germany, have succeeded in entangling a single atom with a single photon in the telecom wavelength range. This constitutes a basic building block for transmission of quantum information over long distance with low loss. The results have raised great attention in the quantum technology community; now they are published in Nature Communications.

The original paper appeared in Nature Communications on May 21, 2018.

Matthias Bock, Pascal Eich, Stephan Kucera, Matthias Kreis, Andreas Lenhard, Christoph Becher und Jürgen Eschner

High-fidelity entanglement between a trapped ion and a telecom photon via quantum frequency conversion

Nature Communications 9, 1998 (2018)  (open access)

Here's the official press release (in German) ("Spukhafte Fernwirkung“ im Physik-Gebäude) of Saarland University.


February: Optical Coherent Control of quantum bits at ultra-low temperatures

Coherent control of the state of a quantum bit (qubit) is a fundamental requirement for any quantum information processing (QIP) system. This control is rather challenging due to the commonly short coherence time of qubits, in particular for qubits embedded in a solid state matrix. We here demonstrate the all-optical coherent control of Silicon-vacancy (SiV) color center qubits in diamond at ultra-low temperatures of a few ten milliKelvin and study the influence of phonon-driven decoherence mechanisms.

The original paper appeared in Physical Review Letters on January, 30, 2018

Jonas N. Becker, Benjamin Pingault, David Groß, Mustafa Gündoğan, Nadezhda Kukharchyk, Matthew Markham, Andrew Edmonds, Mete Atatüre, Pavel Bushev, and Christoph Becher

All-Optical Control of the Silicon-Vacancy Spin in Diamond at Millikelvin Temperatures

Physical Review Letters 120,053603 (2018)

An older version of the paper is available here on the preprint server arXiv (free access).

Here's the official press release of Saarland University ("Der coolste Ort im Saarland").