Initiate the next phase in quantum computing

In the cleanroom, the group manufactures the crystals themselves and integrates them into so-called III-V photonic platforms (see image). (Source: Martin Brandstätter; Copyright: University of Würzburg)

Dr. Andreas Pfenning leads the project. (Source: Martin Brandstätter; Copyright: University of Würzburg)

At Julius Maximilian University of Würzburg (JMU), a technology is currently being developed that could be crucial for the future of quantum technologies: a novel phase modulator that controls light signals extremely quickly and almost losslessly. For the development of this component, the junior research group Ferro35 led by Dr. Andreas Pfenning, Chair of Technical Physics, receives more than 6.6 million euros from the Federal Ministry for Research, Technology, and Space (BMFTR).

Quantum computers, quantum sensors, and eavesdropping-proof communication are considered key technologies of the coming decades. However, despite significant progress, a component essential for scalable photonic quantum systems is still missing: a modulator that precisely influences quantum states without disturbing the delicate light signal. This is exactly where the junior research group is focusing.

A component that makes the difference

Phase modulators are well established in classical optical networks. However, existing solutions are not sufficient for quantum technologies. "We need components that enable high speeds and at the same time exhibit extremely low optical losses," says Pfenning. "This combination does not currently exist—and it is crucial for complex quantum circuits."

The junior research group is therefore pursuing a new approach: they integrate barium titanate (BTO) into III-V photonics platforms, which are already used for efficient quantum light sources. Combining these two material systems is considered technologically challenging but opens up entirely new possibilities for controlling light on a chip.

Crystals from our own production

To make this approach work, the team produces the necessary crystals themselves: layer by layer, in a cleanroom and under high vacuum. The method is called molecular beam epitaxy (MBE) and is among the most precise techniques in materials research. Several MBE systems are already available to the group at the Gottfried-Landwehr Laboratory for Nanotechnology, and another will be set up specifically for Ferro35. "For ferroelectric materials, we need an especially clean processing environment," explains Pfenning. "Even the smallest contaminants can alter the properties of the crystals."

Like Lego: from component to quantum circuit

In addition to the modulator, the group is developing other components necessary for photonic quantum circuits, such as waveguides, couplers, and integrated quantum light sources. These components are initially simulated and then fabricated in the cleanroom.

"We are building a component library that allows us to design, assemble, and directly produce circuits," says Pfenning. "It's somewhat like stacking Lego blocks: when the right element is in the right place, a functional circuit gradually takes shape. The designs developed in this way can be immediately manufactured and tested experimentally."

This not only facilitates development but also opens up new possibilities in teaching. Students will be able to experiment with the models in the future—a playful approach to a highly complex research field.

It will still take some time before fully scalable quantum computers become a reality. However, the components developed in the project could already lay fertile ground earlier. "Fast and low-loss modulators are also interesting for telecommunications," says Pfenning. "Our technology can provide important impulses here."

The "Quantum Futur" funding program

Ferro35 is funded within the framework of the "Quantum Futur 3" program. The initiative of the BMFTR supports young scientists in establishing independent research groups that create new technological foundations for the second generation of quantum technologies. For Dr. Andreas Pfenning, the funding means the opportunity to establish a clearly defined research direction at JMU: ferroelectric quantum photonics.

With Ferro35, a technology platform is being created that aims to contribute to the long-term strengthening of Germany's and Europe's technological sovereignty. The funding includes building its own infrastructure, training scientific personnel, and developing key components for photonic quantum systems.

About the person

Dr. Andreas Pfenning has been leading the Ferro35 junior research group at the Chair of Technical Physics at JMU since 2026. Since the end of 2022, he has been heading the Semiconductor Quantum Photonics working group there and is pursuing his habilitation in experimental physics.

After completing his doctorate, he conducted research as a postdoctoral researcher at the Quantum Matter Institute of the University of British Columbia in Vancouver, where he worked on silicon-based photonic quantum information processing. His current research combines integrated quantum photonics, novel ferroelectric materials, and the development of scalable quantum technologies.