Vortices in superconductors have so far been considered a disruption, as they can impair the superconducting properties. Researchers at the Karlsruhe Institute of Technology (KIT) proved now in experiment that magnetic vortices can be used as controllable quantum systems in certain materials. This means that a previously unwanted phenomenon is becoming a potential resource in quantum technologies, opening up new avenues for the development of quantum computers, highly sensitive sensor systems, and innovative approaches in materials research. The results have been published in Nature. (DOI: 10.1038/s41586-026-10441-7)
Superconductors are materials that, under certain conditions, conduct electricity with zero resistance, entirely expelling magnetic fields. However, once the magnetic flux exceeds a critical threshold, magnetic fields start to penetrate into the material as tiny, quantized vortices. Such vortices have so far been considered unwanted disruptive factors, as they have an energy-draining effect, limiting the efficiency of superconducting systems.
Material Structure Enables Quantum Effects
The current study conducted by a research team led by Professor Ioan M. Pop at KIT’s Institute for Quantum Materials and Technologies (IQMT) documents a completely new behavior of magnetic vortices in superconductors. The researchers investigated strongly disordered superconducting thin films made from granular aluminum layers that are close to the superconductor-to-insulator transition. In this kind of material, the vortices lose their disrupting properties and form stable low-loss states, which can be described in terms of quantum mechanics.
Physically, this effect is due to the particular structure of the material: Granular aluminum consists of nano-scale superconducting islands separated by non-superconducting regions. This configuration forms a complex energy landscape with local minima between which a vortex can move back and forth by quantum tunneling. Based on these stable two-level systems, the observed quantum states can develop.
Once a Disrupting Factor, Now a Qubit
"This is an exciting finding for us, both because it reveals new fundamental quantum behavior and because of its potential implications for quantum technologies," said Ameya Nambisan from the IQMT. “Our results show that vortices are not only controllable, but also behave just like artificial atoms with two clearly distinguishable states,” said Dr. Simon Günzler from the IQMT.
“Thus, they meet a key requirement for the use as qubits in quantum technologies,” added Pop. “Another outcome from the study is that under favorable conditions, even phenomena that have been considered disruptive for a long time, can become valuable resources. This opens up completely new prospects for the design of future quantum systems.”
Not only could the researchers identify these vortex qubits, but, using microwave measurements and methods from quantum electrodynamics, they were also able to specifically manipulate them and read them out. The coherence and relaxation times measured are in the microsecond range and thus comparable to those of well-known superconducting qubit systems. This secures vortex qubits a place among the most extraordinary candidates for applications in quantum technology to date.
New Prospects for Technology and Research
In the long term, these systems can serve as novel qubits, which do not have to be synthesized but are the result of harnessing intrinsic material properties. Besides potential applications in quantum information technology, new approaches to the experimental research of complex materials can be taken. This includes the future use of vortex qubits as highly sensitive probes to accurately analyze microscopic properties in superconductors.
“Although there are still open questions regarding the technical implementation and scalability of vortex qubits, our findings clearly demonstrate that in physics, even phenomena previously perceived as unwanted can become useful resources for quantum mechanics,” said Pop. Superconducting vortices are exemplary of how new ways for future technologies can open up.
The study was conducted in collaboration with researchers from the universities of Antwerp and Ulm.
Original publication
Ameya Nambisan, Simon Günzler, Dennis Rieger, Nicolas Gosling, Simon Geisert, Victor Carpentier, Nicolas Zapata, Mitchell Field, Milorad V. Milošević, Carlos A. Diaz Lopez, Ciprian Padurariu, Björn Kubala, Joachim Ankerhold, Wolfgang Wernsdorfer, Martin Spiecker & Ioan M. Pop: Quantum coherent manipulation and readout of superconducting vortex states. Nature, 2026. DOI: 10.1038/s41586-026-10441-7.
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