Episode Details

In this episode of ML4Q&A, hosts Chandana Rao and Mira Sharma speak with Dr. Lars Schreiber (RWTH Aachen University), along with his PhD students Mats Volmer and Max Beer, about the challenges of scaling silicon-based spin qubit quantum computers. Lars Schreiber shares insights into why semiconductor platforms despite their technological maturity have not yet achieved large-scale quantum systems.

The conversation explores the practical realities of building spin qubit devices, from material imperfections and device variability to the difficulty of controlling millions of qubits. Mats and Max discuss their work on conveyor-style spin-qubit shuttling and T-junction architectures for routing qubits in two dimensions, explaining how moving electrons across a chip can enable scalable designs while introducing new challenges such as valley splitting and decoherence. They also discuss the surprising material physics that emerges when quantum informations starts to move.

The episode also examines how these research ideas are transitioning into real-world technology through the startup Arque Systems, highlighting the shift from academic prototypes to industrial-scale quantum hardware.

Listen to the full episode to explore the path toward scalable semiconductor quantum computing.

0:00:04 Introduction & guest overview 0:02:04 Career journeys: from semiconductors to spin qubits 0:08:44 Life as an experimental quantum PhD student 0:11:32 Teaching quantum technology at RWTH Aachen 0:15:05 What is a spin qubit? Silicon vs Galium-Arsenide 0:21:01 Qubit encodings, scalability & conveyor-mode shuttling 0:31:38 Valley splitting: the key material challenge in silicon devices 0:43:05 Measuring spin states through coherent shuttling 0:52:18 T-junctions and 2D quantum routing architectures 1:05:31 From academic research to Arque Systems startup 1:09:26 Future outlook, lessons & advice for researchers