Fraunhofer IPMS and the Max Planck Institute of Quantum Optics (MPQ) have achieved significant results in generating arbitrary light distributions, which are also relevant to atomic quantum computing. Spatial light modulators can be used to stimulate a large number of atoms in desired positions at the same time via laser beam. Localized in this way, they become switchable information carriers for quantum computers or for other applications in quantum metrology and quantum simulation, marking a major stride toward scalable quantum systems. Quantum computers based on charged or neutral atomic qubits offer a wide array of advantages over alternative technologies. They permit intrinsically high quality in the in-dividual qubits — the charge carriers in the computer system — and thus achieve excellent coherence times and gate quality. For neutral atoms to become qubits, they need to be manipulated with high-precision lasers in their quantum states. Strontium atoms are among those used to generate qubits in atomic quantum computers. These atoms are manipulated in the UV range, as important electronic transitions that can be used to excite their quantum states can only be achieved in the ultraviolet spectral range. The Max Planck Institute of Quantum Optics has been researching how to arrange and address neutral atoms for some time now. The hardware needed for spatial modulation of the UV rays that are required is still under development. Currently, there is a lack of scalable and sufficiently precise solutions that can be used to excite qubits individually. Researchers working on the project have now demonstrated that high-quality optical dot grids can be realized in the relevant UV wavelength range with spatial light modulators (SLMs) based on piston mirror arrays. Fraunhofer IPMS has special expertise in these kinds of arrays. In an experiment led by the Max Planck Institute of Quantum Optics, the strontium atoms used to generate qubits are laser-cooled and trapped in optical dot grids. The project joined the partners’ complementary expertise in a bid to advance into new realms of atomic quantum computing. To this end, Fraunhofer IPMS further developed a micro-mirror-based SLM that can be used to generate programmable and highly precise patterns in the nanometer range. The phase patterns generated can then be converted into any kind of laser beam schema using suitable optics. As part of the project, a relevant element was provided to the Max Planck Institute of Quantum Optics for testing. Its performance was demonstrated across all fields. Future work will be geared toward trapping the tiny atoms in the focal points of the laser beams and holding them in certain positions. Laser beams acting in this way are known as “optical tweezers.” The atoms’ internal quantum states are then manipulated using high-precision pulses to perform quantum logic operations for quantum calculations. Dr. Michael Wagner from Fraunhofer IPMS says of the successful project: “Our SLM systems enable light modulation up to the deep UV range. Micromirror technology offers a wide range of advantages over liquid crystal-based light modulators, such as UV compatibility, higher modulation speeds up to the megahertz range and polarization-independent work.” Alongside Fraunhofer IPMS demonstrating that SLMs are suitable for quantum optical experiments in the UV range and the Max Planck Institute successfully qualifying the technology for the experimental set-up, the project also focused on evaluating the accuracy of the phase modulation. Phase control in a range significantly below one one-hundredth of a wavelength was demonstrated, meeting the most stringent requirements that apply to the quality of optical tweezers. The next step on the way to the quantum system The use of micromirror-based SLMs for pattern generation and qubit control opens up a whole new dimension in relation to accuracy and scalability. The demonstrator devel-oped and the project results are key parameters for targeted further development of the SLM-technology for applications in the quantum field. Going forward, they may serve as a sound basis for realizing an apparatus for addressing the atoms. One of the next goals is to develop SLMs that enable parallel generation of several thousand focused laser beams in the ultraviolet spectral range. Increasing the system’s speed is another area of focus. The 1 kHz that has been achieved at present is merely a starting value for significantly faster future modulators. More information can be found on the Fraunhofer IPMS website.  

Fraunhofer IPMS has developed a new key management system (KMS) specifically designed for use in quantum-secure networks. The system enables the secure exchange of secret keys and ensures reliable, secure data distribution across large-scale network infrastructures. In view of the computing power of future quantum computers, traditional methods of key distribution, such as RSA and Diffie-Hellman, are under increasing pressure. To mitigate this risk and ensure secure digital communication, Fraunhofer IPMS’s KMS software employs quantum key distribution (QKD) technology, which is rooted in quantum principles. This enables individual point-to-point connections to be linked into a scalable and secure network, allowing cryptographic keys to be distributed symmetrically and in a controlled manner across multiple nodes and domains. As a result, an additional end-to-end security and communication layer is created for critical infrastructures. QKD not only enables secure key exchange, but also detects any eavesdropping attempts, ensuring that interference is immediately reported to the relevant parties. Integrating QKD into a cybersecurity strategy therefore provides the highest possible level of protection against emerging quantum threats. Special features of the Fraunhofer IPMS Key Management System (KMS) Fraunhofer IPMS is a reliable partner for companies that require quantum-secure communication. With its many years of expertise, innovative technologies and cutting-edge research in quantum key distribution (QKD), the institute helps companies to safely overcome the challenges of quantum computing and to build networks that will stand the test of time. “Our key management system is at the heart of complex QKD networks,” explains Dr Alexander Noack from Fraunhofer IPMS. “It coordinates key requests, generates physically secure keys, reliably distributes them, and manages their lifecycle.” Centralized control via a modern, container-based architecture enables transparent, flexible and efficient management of even large networks. Thanks to its high scalability, the platform can be used in research and demonstration environments, as well as in large, multi-node networks. Fraunhofer IPMS is setting an important milestone for secure communication in the future with its system, which complies with the ETSI-GS-QKD-014 standard. High-performance quantum random sources ensure the highest security standards, and a QKD-encrypted communication layer secures key exchange, even over public networks. Fraunhofer IPMS is currently developing an inter-domain interface via shared trusted nodes to enable the future networking of multiple QKD domains. This will enable seamless interoperability and network expansion. Possible applications and benefits The KMS developed by Fraunhofer IPMS extends quantum key distribution from simple point-to-point links to full network infrastructures. This enables a wide range of sectors to benefit, including telecommunications and metro networks, critical infrastructure such as energy, transport and healthcare, data centers and cloud providers, government and research networks, as well as Industry 4.0 environments. Companies and public authorities can thus secure multiple sites simultaneously, without the need to install dedicated point-to-point connections for each individual link. “We have already successfully demonstrated the performance of our system in the QuNET+MOBIXHAP project, which explored various scenarios ranging from simple laboratory networks to complex topologies. In addition, our inter-domain interface, currently under development, will enable secure communication across domain boundaries and provide investment security for ‘Q Day’,” explains Dr Noack. Further information on quantum communication technologies at Fraunhofer IPMS and the new communication management system can be found on the institute’s website.

Fraunhofer IPMS and the Max Planck Institute for Chemical Physics of Solid States CPfS are introducing a new CMOS-integrated platform for quantum sensing. Patrick Engelmann, project leader at Fraunhofer IPMS, highlights the benefits of the new approach: “The newly developed CMOS-based platform for quantum sensing can be easily operated at room temperature due to NV technology, where otherwise complex cryotechnology would be required. By integrating the light source, detector, microwave, and readout on a chip, the system is significantly miniaturized and consumes very little energy. Furthermore, we can achieve spatial resolution in the micrometer range using multi-channel arrays instead of single measurement points. The system is robust and portable, as it does not require lasers or optics.” The development of these CMOS-integrated quantum sensors opens new horizons in various fields, from geophysics for exploring deformations of the Earth’s magnetic field to medicine for heart and nerve monitoring, and potentially as an interface for brain-machine interaction. This technology addresses challenges that have not been resolved previously, such as portable magnetic field quantum sensors for rapid, highly sensitive on-site analyses and simplified laboratory workflows. At Fraunhofer IPMS, the required CMOS backplane is designed and manufactured in a commercial semiconductor facility. Afterwards, OLED light sources will be integrated onto the chip at the institute. The precise alignment of the NV diamonds to the sensor pixels is crucial for optimal measurement results. The work builds on the available expertise at the institute for the integration and manufacturing of OLED-on-silicon devices, specifically based on the so-called “bi-directional” microdisplays with image capture and playback functionalities on a chip. The MPI CPfS is engaged in the joint project with measurement methodology, as well as the investigation of quantum optical material in the form of NV diamonds and alternative materials for this application. So far, the joint integration of OLED and antenna, as well as the excitation of the NV center in a technology demonstrator, has been demonstrated. Work is still ongoing on the complete CMOS integration of the sensor system, including photodetectors and the complete readout circuit. Initial industry partners have already expressed interest. Verification in initial research applications is expected within three to four years. Upon positive validation, the platform can be quickly adapted to specific applications and transitioned to pilot production.