FBH presents developments for quantum technologies at EQTC 2023

Quantum technologies promise nothing less than a technological revolution in areas such as sensor technology, communication, and computing. This tremendous potential for innovation is also reflected by the European Quantum Technology Conference (EQTC), which will be held in Hannover from October 16 - 20, 2023. The Ferdinand-Braun-Institut (FBH) will present current developments and results during the international conference with a wide range of scientific contributions. At the accompanying exhibition, FBH will exhibit at the Berlin-Brandenburg joint booth (F08 - F10) starting on October 17.

The Ferdinand-Braun-Institut possesses the complete value chain in-house, from chip design and processing to micro-integrated, particularly compact and robust modules and systems. At EQTC, it will showcase its comprehensive range of services: from integrated photonic devices for quantum communication and information processing, which can be used to precisely control light, to atom-based quantum technologies and integrated quantum sensors. Research and development activities in the field of quantum technologies are carried out in particular by the four Joint Labs in which FBH cooperates with Humboldt-Universität zu Berlin. With these joint research groups, FBH successfully bridges the gap between basic and application-oriented research.

Laser modules and systems for quantum sensor technology

The Berlin-based research institute develops and delivers, among other things, complex and robust laser modules for quantum sensors used on sounding rockets, the International Space Station (ISS), and on satellites. These modules deliver 500 mW in a single-mode fiber at > 20 % conversion efficiency (electrical to optical) and offer a narrow intrinsic linewidth < 1 kHz. They enable quantum sensing applications in fundamental physics, geo- and environmental physics, and timing and navigation. Core components are diode lasers with wavelengths ranging from 620 to 1180 nm. For all systems, especially for space projects, FBH carries out extensive reliability and environmental tests.

FBH laser modules are also used to set up compact quantum sensors and optical frequency references (OFR) for use in space. For example, an ultra-compact (volume < ½ liter) autonomous frequency reference based on the D2 transition in rubidium at 780 nm has been demonstrated. It achieves a short-term stability of 1.7 x 10^-12 at 1 second. The FBH also develops the corresponding systems that are based on the 778 nm two-photon transition and which are promising candidates for global navigation satellite systems. In addition, they are used in optical calibration and as absolute frequency references in atom-based quantum technology.

Quantum laser modules – for 3D quantum imaging

For hyperspectral imaging in the mid-infrared range (MIR) and quantum OCT (optical coherence tomography), FBH is developing hybrid-integrated, miniaturized quantum light modules. They are the centerpieces of sensor systems based on "undetected photons." For this purpose, the researchers have developed special laser diodes and micro-optical elements that are integrated into a compact package together with a nonlinear optical crystal. These quantum light modules generate entangled photon pairs that interact in a nonlinear interferometer. This makes the technically challenging MIR spectral range accessible, with measurements performed exclusively in the near-infrared range. Due to the entanglement, neither detectors nor additional radiation sources are needed in the MIR.

Photonic-integrated circuits – basis for quantum operations

Photonic quantum computing uses light particles to generate and measure photonic resource states. A promising approach is provided by photonic cluster states. Integrated photonic circuits are designed to perform the required quantum operations and generate the photonic cluster states. FBH has developed a photonic platform made from AlGaN heterostructures for electro-optically controlled circuits that are suited for fast and precise on-chip operations and measurements.

To realize computationally intensive resource states, one of the Joint Labs is investigating how to create photonic cluster states with optically active spin defects. The scientists are designing and fabricating nanophotonic spin-photon interfaces in diamond. For example, they recently fabricated a sawfish-like resonator that holds great potential to generate entangled photons with high efficiency. This has been demonstrated in simulations and is now to be confirmed experimentally.