Scientists are working on the totally bug-proof communication – 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 small 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.
Quantum networking is based on the transmission of single photons being used as “flying” quantum bits. The probability to detect a single photon upon fiber transmission decreases exponentially with increasing fiber distance. It is therefore necessary, to use photons with specific wavelength such that transmission within a range of 10 to 100 km is possible via optical fibers. Nevertheless, the quantum signal has still to be repeated as in classical communication channels.
However, such “quantum repeaters” are fundamentally different to repeaters of classical communication as they have to bridge the intermediate distance by means of quantum mechanical effects. The building block of such a technology is the interference of two photons stemming from remote quantum emitters. “In this experiment, we use semiconductor nanostructures as sources of single photons.
They have the big potential to emit single photons at record rates”, says Jonas Weber. The PhD student at the University of Stuttgart is in charge of the handling of the quantum light sources, therefore of the generation and interference of the single photons. “High emission rates are crucial for high data transfer”, further explains Jonas Weber.
The typically used nanostructures, which are referred to as quantum dots, emit photons in a wavelength range which is not compatible with optical fibers. To still exploit the advantages and perspectives of quantum dots, the Quantum Optics group at Saarland University, led by Prof. Christoph Becher, built two independent quantum frequency converters.
With such devices, the emitted photons are mixed with strong laser beams, such that their wavelength is converted and thus prepared for transmission in optical fibers. “Only because of this manipulation, the photons can be transmitted over 10-100 km fiber distance. Without this procedure, every kilometer the signal would have to be repeated.
This wouldn’t be feasible at all”, says Benjamin Kambs, the PhD student in the group of Prof Becher, who was in charge of building and optimizing the two frequency converters.
The physicists were able to show that the necessary photon manipulation does not compromise the quantum mechanical nature of the light. Based on that premises, the emitted photons were sent through 2 km optical fiber and still successfully brought to interference. This is a non-negligible fact, given the rather fragile nature of such quantum states.
“This complex experiment was only possible because of the long-lasting collaboration between Saarland University and University of Stuttgart. It was successful due to a remarkable team work and it shows that quantum dots in combination with quantum frequency conversion are a viable platform for future quantum repeater scenarios”, says Peter Michler, head of the IHFG, University of Stuttgart.
Prof. Dr. Peter Michler, Universität Stuttgart, Institut für Halbleiteroptik und Funktionelle Grenzflächen, Tel.:+49 (0)711/685-64660, firstname.lastname@example.org
Publication: J. H. Weber, B. Kambs et al., Two-photon interference in the telecom C-band after frequency conversion of photons from remote quantum emitters, Nature Nanotechnology, 2018; https://doi.org/10.1038/s41565-018-0279-8
Andrea Mayer-Grenu | idw - Informationsdienst Wissenschaft
Genetic code for stem cell heart repair detected
06.07.2020 | Universität Rostock
Spintronics: Faster data processing through ultrashort electric pulses
02.07.2020 | Martin-Luther-Universität Halle-Wittenberg
Solar cells based on perovskite compounds could soon make electricity generation from sunlight even more efficient and cheaper. The laboratory efficiency of these perovskite solar cells already exceeds that of the well-known silicon solar cells. An international team led by Stefan Weber from the Max Planck Institute for Polymer Research (MPI-P) in Mainz has found microscopic structures in perovskite crystals that can guide the charge transport in the solar cell. Clever alignment of these "electron highways" could make perovskite solar cells even more powerful.
Solar cells convert sunlight into electricity. During this process, the electrons of the material inside the cell absorb the energy of the light....
Empa researchers have succeeded in applying aerogels to microelectronics: Aerogels based on cellulose nanofibers can effectively shield electromagnetic radiation over a wide frequency range – and they are unrivalled in terms of weight.
Electric motors and electronic devices generate electromagnetic fields that sometimes have to be shielded in order not to affect neighboring electronic...
A promising operating mode for the plasma of a future power plant has been developed at the ASDEX Upgrade fusion device at Max Planck Institute for Plasma...
Live event – July 1, 2020 - 11:00 to 11:45 (CET)
"Automation in Aerospace Industry @ Fraunhofer IFAM"
The Fraunhofer Institute for Manufacturing Technology and Advanced Materials IFAM l Stade is presenting its forward-looking R&D portfolio for the first time at...
With an X-ray experiment at the European Synchrotron ESRF in Grenoble (France), Empa researchers were able to demonstrate how well their real-time acoustic monitoring of laser weld seams works. With almost 90 percent reliability, they detected the formation of unwanted pores that impair the quality of weld seams. Thanks to a special evaluation method based on artificial intelligence (AI), the detection process is completed in just 70 milliseconds.
Laser welding is a process suitable for joining metals and thermoplastics. It has become particularly well established in highly automated production, for...
02.07.2020 | Event News
19.05.2020 | Event News
07.04.2020 | Event News
06.07.2020 | Health and Medicine
06.07.2020 | Social Sciences
06.07.2020 | Materials Sciences