This expertise is also reflected in the InnoQT innovation network, which connects the regional players and is open to new partners. This network links university and non-university research with industry partners, from start-ups and medium-sized companies to large, established firms.
The Quantum Future Academy serves to attract young talent and to promote networking throughout Europe. It allows students from 29 countries to gain insights into applied quantum technologies. Berlin researchers also make important contributions to exciting space projects. For example, they are not only working on optical atomic clocks that make more precise satellite navigation possible. As part of the BECCAL experiment, they are also helping to realize a highly sensitive Bose-Einstein condensate on board the International Space Station.
From Theory to Innovative Research
The working group of Jens Eisert at the Dahlem Center for Complex Quantum Systems of the Freie Universität Berlin analyzes the theoretical problems of realistic quantum computers. The researchers pose questions about what kinds of quantum communication protocols can be conceived and how to develop a vision of the quantum internet. A recurrent theme is the issue how one can certify the correct functioning of components. Even if this kind of research is being pursued with theoretical methods, the work is often linked to quantum optical experiments.
The Nanooptik AG led by Prof. Oliver Benson at Humboldt University Berlin investigates the theory of light-matter interaction. The researchers analyze fundamental question with new methods, such as quantum emitters in solids that generate single photons or exchange such photons with each other. Optical methods make it possible to verify the theories of quantum physics with tremendous precision. Particularly important phenomena are entanglement, wave-particle dualism, and other quantum paradoxes such as the quantum Zeno effect.
The group also works on new quantum technologies, such as single quantum light sources on scanning probes for high-resolution spectroscopy and microscopy. They also develop photon sources and algorithms for a quantum cryptography. Together with local partners at universities, research institutions and industry, these new approaches are already being implemented in test tracks and demonstrators. They also perform quantum-enhanced optical precision measurements and develop ultra-stable optical systems to test fundamental physics, even in space.
At the Institute for Solid State Physics of Technical University Berlin, Prof. Stephan Reitzenstein’s research group in optoelectronics and quantum devices develops nanophotonic devices based on semiconductor heterostructures. The infrastructure of the Center of Nanophotonics at the TU Berlin is available for their nanofabrication. One focus of the work is the study and targeted application of light-matter interactions in quantum optical regimes, which provide novel functionalities in quantum devices. One example are single photon sources for quantum cryptography. For this purpose, individual semiconductor quantum dots are integrated into nanophotonic structures and optimised for their emission properties using in situ electron beam lithography, a unique technology specially developed by the working group. Further work aims at quantum networks and at integrated quantum photonics and ultimate micro- and nanolasers with disappearing laser thresholds. The latter are not only very interesting from the perspective of theoretical physics but can also be used as nanophotonic hardware components in the field of neuromorphic computing.
The DLR-Institute of Optical Sensor Systems develops active and passive optical sensor systems for spaceborne and airborne applications as well as for robotic systems. Quantum technologies are vital for the institute‘s mission. The research activities cover novel quantum materials, sensors and detectors with quantum-limited sensitivity. Quantum technologies of particalur interest are quantum light sources and quantum memories, as well as on applications of such devices in quantum communication and computing.
The Ferdinand-Braun-Institut, Leibniz-Institut fuer Hoechstfrequenztechnik (FBH) is very active in the field of modern quantum components. Together with Humboldt University Berlin, they are working on state-of-the-art laser technologies. In 2017, its technology was used in the first success in generating a special state of matter called a Bose Einstein condensate aboard a sounding rocket. These and other quantum technologies are used to research quantum optical sensors and other components for secure communication, quantum simulation and computing, quantum-assisted imaging, and spectroscopy. Coherent radiation sources are important for quantum optical applications and as well robustness and reliability for space technologies. For this purpose, FBH uses its competences in the fields of semiconductor, microwave and diode laser technology. This also includes hybrid photonic modules, integrated quantum sensors or nanostructured diamond systems. Such components as well as nonlinear optical quantum devices are relevant for quantum networks.
The Fraunhofer Institute for Telecommunications, Heinrich Hertz Institute HHI has comprehensive experience and expertise in designing, developing and prototyping photonic components and systems towards quantum communication and sensing. Their foundries offer rapid and flexible development and fabrication of photonic integrated circuits (PICs) and components. With the innovative PolyBoard platform, they offer hybrid integration of low loss free-space sections and bulk materials, such as Faraday rotators and nonlinear crystals for quantum applications, into PICs via micro-optical benches. For R&D purposes they offer a quantum testbed facility comprising optical free-space and fiber links.
The experts at Fraunhofer Institute for Reliability and Microintegration IZM are using their expertise in photonic system integration and miniaturization to find new solutions for the quantum age. This includes the integration of optical waveguides, design-based processing of tailored refractive index profiles, generation of strong evanescent fields in the immediate vicinity of quantum emitters, the trapping of neutral atoms in such evanescent fields or the coupling of optical fibers using innovative interconnection techniques. These technologies are also used for the production of future all-glass quantum chips.
Spin qubits in semiconductor materials are promising candidates as basic elements for quantum computers. For this reason, researchers at Leibniz Institute for Crystal Growth (IKZ) grow isotopically enriched thin-strained silicon layers between SiGe barriers by molecular beam epitaxy. Such a layer forms a quantum well for a two-dimensional electron gas. Top gates on such semiconductor structures electrostatically form the quantum dots which are hosting single electrons for spin manipulation.
The Max Born Institute for Nonlinear Optics and Short Pulse Spectroscopy (MBI) conducts basic research in laser-matter interaction. Taming the unusual propagation scenarios of light in novel photonic devices offers unprecedented opportunities where optical quantum effects can be exploited. In the next years, the femtosecond-laser microprocessing group together with the group for theoretical optics & photonics will focus on making such chips reprogrammable, holding the promise to provide versatile optical circuits for classical and quantum-based applications.
The quantum technology activities at Paul-Drude-Institut für Festkörperelektronik (PDI) are based on expertise in semiconductor nanostructure epitaxy as well as in phononics, quantum photonics, quantum transport and the manipulation of single atoms. Highlights combining these aspects of quantum technology include their hybrid opto-mechanical single-photon sources and spin processors. These rely on surface acoustic waves that transport spin-polarized electronic excitations and inject them into two-state centers, where they recombine and emit single photons. The researchers are also working on quantum circuits on a chip. This leads to quantum structures on semiconductor surfaces on an atomic scale and allows complete control of their properties. The goal is to implement such structures in quantum information technology in the future.
The Physikalisch-Technische Bundesanstalt (PTB) works on several fields of quantum technology, with a focus on quantum sensing and metrology. It supports the transfer of quantum technology from science to applications in industry and academia. The new Quantum Technology Competence Center coordinates these activities. At PTB’s site in Berlin the activities focus on quantum magnetometry and cryogenic sensors, for instance highly sensitive SQUIDs and optical magnetometry for metrology, fundamental research, medical applications and beyond. It also provides an exceptionally well controlled environment for sensing smallest magnetic fields. This infrastructure is accessible to external partners.
The Zuse Institute Berlin (ZIB) is an interdisciplinary research institute for applied mathematics and high-performance computing. The Computational Nano Optics group investigates and applies numerical methods for the simulation of light-matter interactions in nanoscale devices. A highly topical field of application is optical quantum technology: modeling and simulation are used for the interpretation of experimental results as well as for the effective design of future technologies, such as quantum communication devices and quantum computers.
Industry with innovative ideas
As a startup in secure communication, GoQuantum c/o Factory Works GmbH develops connectivity devices for post-quantum communication. The algorithms used are not affected by quantum computers which can break standard encryption. This technology also uses quantum random number generators for extra-secure keys and permits customer-specific security implementations for 5G and IoT networks.
JCMwave GmbH develops software for fast and accurate optical simulations. For use in quantum technologies the software comprises special features such as the simulation of quantum dot light sources, the determination of the Purcell effect, or the calculation of resonator field modes.
Menlo Systems GmbH provides complete laser systems for cold atom experiments that can be used in different applications. Such setups are necessary parts of optical clocks, quantum simulations or quantum computing experiments based on cold atoms or ions. The company also has experience in optical frequency combs, cavity-stabilized lasers, femtosecond lasers and terahertz systems.
For some years already, M Squared Laser Limited has been at the heart of the international quantum supply chain. Its experts develop components, sub-systems and sensors for commercial quantum applications. The company provides the world’s purest light to enable scientific progress and power industry. Its lasers and cutting-edge photonics systems are working to realise the potential of the coming quantum age, deliver advances in healthcare and provide the scientific understanding to help halt climate change. M Squared also specialises in the development of extremely stable and robust lasers with expertise spanning CW to fs, and DUV to THz wavelengths.
The lasers of Picoquant GmbH also find application in quantum technology. These include Hanbury-Brown-Twiss set-ups to study single photon sources, quantum communication and quantum key distribution (QKD), Bell state measurements, or experiments on quantum gates for future quantum computers.
QUARTIQ GmbH is a pioneer in the development of open hardware and software solutions for quantum technology applications. It supplies research and metrology institutes worldwide with custom designs and also provides development and integration in collaborative industrial research projects, such as transportable and robust optical atomic clocks. The firm also works on algorithms and components for high-performance measurement and control tasks.
The laser diodes from eagleyard Photonics GmbH have also found their way into space. The Adlershof-based subsidiary of TOPTICA Photonics AG develops and manufactures laser diodes for a wide range of applications including analytics, automotive technology, and industrial applications as well as aerospace. For quantum technology applications they offer single frequency lasers with a line width down to below 1 MHz.
Quantune Technologies GmbH develops and markets microscopic infrared laser spectrometers for highly innovative consumer products based on patented quantum cascade laser and photoacoustic technologies.
The article was written by Dirk Eidemüller.