Speaker: Prof. Raimer Dumke, NTU Singapore
Title: Integrating Atoms and Superconductors - Towards a Unified Quantum Hardware Architecture
Abstract: Quantum technology is evolving toward hybrid architectures that unite the long coherence and precision of atomic systems with the high-speed control and scalability of superconducting quantum circuits. I will discuss innovations enabling hybrid atom–superconductor coupling, including experiments transporting ultracold atoms into dilution refrigerators, demonstrating lifetimes exceeding 10 minutes under cryogenic conditions, and ongoing work toward Rydberg-transmon coupling. On the superconducting side, the presentation covers 5-20 qubit devices, scalable RFSoC-based control electronics, and their integration within cloud-accessible quantum computing platforms.
Location: WMI Seminar Room 143
Online: Zoom Link, Meeting-ID: 634 3633 2812, Kenncode: 642403
The Nobel Prize in Physics in the IYQ 2025 honors the achievements of John Clarke, Michel H. Devoret, and John M. Martinis in the field of macroscopic quantum phenomena and celebrates the centenary of quantum mechanics. The realization of quantized electrical circuits has enabled, among other things, the development of superconducting qubits, a key technology for quantum computers. Typically, quantum effects such as tunneling through classically insurmountable barriers can only be observed on extremely small scales. This makes states such as superpositions possible, in which microscopic particles can exist on both sides of a barrier. In the 1970s, the award-winning researchers at the University of California, Berkeley, successfully demonstrated this tunneling effect on macroscopic scales and created superpositions based on tunneling through Josephson junctions. Here, at the Walther Meißner Institute, researchers follow the footsteps of the Nobel laureates and further develop superconducting qubits.
In the evening of Monday, 06.10.2025, WMI opened its doors to the general public in the context of the 2025 International Year of Quantum Science and Technology (IYQ) and the outreach activities of the Munich Quantum Valley.
Forty-seven participants visited our laboratories to learn about superconducting qubits, nanofabrication, spin systems, and quantum communication. The event began with a presentation by our director, Peter Rabl, who shared the history behind physics at the lowest temperatures.
The Quantum Computing Group at WMI presented a coherent control method for superconducting fluxonium qubits, employing a Purcell‑protected flux line featuring a low‑pass filter. This approach closes the control hannel at the qubit transition frequency, reducing qubit decay while enabling fast, high‑fidelity control via parametric subharmonic driving at integer fractions of the transition frequency. The scheme supports coherent control using up to 11‑photon subharmonic drives, with observed Rabi frequencies and induced frequency shifts aligning closely with theoretical models. A three‑photon subharmonic drive is functionally equivalent to on‑resonance driving, achieving single‑qubit gate fidelities exceeding 99.94%. This demonstration establishes a scalable and wiring‑efficient control architecture for fluxonium‑based quantum processors.
Quantum computers are not yet powerful enough to outperform classical computers on complex problems beyond simple demonstrations. To tackle computational challenges of high interest, quantum computers must grow from a few qubits to thousands. Scaling up current quantum processors, such as those based on superconducting qubits, introduces new challenges, such as limited physical space and a growing number of control lines. Our work presents a superconducting qubit architecture designed to address these challenges using frequency-modulated coupling elements. The elements connect multiple qubits and readout components, reducing the number of required control lines without sacrificing controllability. Using a single coupling element, we successfully demonstrate two-qubit interactions, unconditional qubit reset to the ground state, leakage elimination to higher-energy states, and qubit readout. These operations are crucial for building scalable quantum computers and are selectively controlled via the drive frequency of the coupler. This work advances the scaling of quantum computers based on superconducting qubits beyond small-scale applications.
The European consortium OpenSuperQPlus (OSQ+) is making significant strides toward building Europe’s first 100-qubit quantum computer by 2026 — with impressive progress in both qubit number and quality thanks to all its partners. TU Delft has released two scalable prototypes to the cloud, with test benching performed by OrangeQS. Simultaneously, Finnish and German partners, including VTT, IQM Quantum Computers, and Fraunhofer EMFT, are progressing with scaling and chip manufacturing. We are happy that we at the WMI continue to push larger qubit numbers with a 17-transmon QPU.
Full press release
🎯 Want to learn more? Join us at the SQA 2025 Conference in Delft, 25–28 August. We’ll discuss benchmarking, calibration, and the path to 100 qubits—with an impressive line-up of international experts, including contributions from WMI.
