DQC Seminar Series: Scalable Register-Based Trapped-Ion Quantum Processors with Near-Field Microwave Gates

The Trapped-Ion Quantum Engineering group at Leibniz University of Hannover (LUH) and the Physikalisch-Technische Bundesanstalt (PTB) studies the physics of trapped ions in radiofrequency and Penning traps. We provide an overview of the group and report on recent results and projects. We focus on our efforts to combine chip-integrated near-field microwave conductors for laser-free quantum logic gates and the Quantum Charge-Coupled Device (QCCD) architecture. This register-based architecture provides a scalable platform for trapped-ion quantum processors, enabling all-to-all connectivity between the atomic ion qubits. In the past, all the fundamental building blocks of the architecture have been successfully demonstrated. However, combining the QCCD architecture with microwave near-field control into scalable devices for quantum information processing is a current research topic. We present our latest three generations of surface-electrode traps addressing this challenge for up to 50 trapped-ion qubits. We highlight the trap design and simulation, with a focus on radiofrequency (RF) junctions, co-wired storage registers, and chip-integrated microwave conductors. We further provide insights to enhance our traps with integrated nanophotonics, optimized electrode structures, and cryogenic control electronics. We acknowledge funding by the Quantum Valley Lower Saxony (QVLS) Q-1 project, the German Federal Ministry of Research, Technology and Space (BMFTR) through the MIQRO and ATIQ projects, and the European Union via the MILLENION project (HORIZON-CL4-2022-QUANTUM-01-SGA).