One-Superconductor Josephson Junctions Could Transform Quantum Computing
At the core of modern quantum computers lies a deceptively simple device: the Josephson junction.
Traditionally, it consists of two superconductors separated by an ultrathin barrier. Despite the separation, electrons move in unison, allowing current to flow precisely with no energy loss. This synchronized motion underpins today’s most advanced quantum processors and contributed to the 2025 Nobel Prize in Physics.
A surprising experiment
Now, researchers report a surprising twist. They provide the first experimental evidence that Josephson junction-like behavior can emerge even with only one true superconductor.
The team built a layered structure using superconducting vanadium and ferromagnetic iron, separated by a thin layer of magnesium oxide.
Conventional physics suggests this setup should not act like a Josephson junction. Iron is not a superconductor, and its magnetism usually disrupts the delicate electron pairing needed for superconductivity.
Yet electrical measurements told a different story. Current patterns closely matched those of a conventional Josephson junction. Somehow, superconducting behavior from vanadium crossed the barrier and organized electrons in iron, creating synchronized motion between the two materials.
Evidence from electrical noise
Key proof came from analyzing electrical ‘noise.’ While the current seems smooth at a large scale, it actually arrives in bursts of electrons.
The pattern of these fluctuations reveals whether electrons act independently or in coordinated groups. In the vanadium-iron device, electrons moved in large, synchronized packets inside the iron layer. This collective motion is a hallmark of Josephson junctions and confirms superconducting correlations where none were expected.
Magnetism meets superconductivity
The role of iron makes this finding remarkable. Superconductivity usually pairs electrons with opposite spins. Ferromagnets like iron favor aligned spins. These opposing tendencies normally clash.
The experiment suggests iron developed an unconventional superconductivity involving same-spin electron pairs. This state was strong enough to couple back with vanadium, making the system behave as if both sides were superconductors.
Implications for quantum technology
This one-superconductor Josephson junction could have far-reaching consequences.
Simplifying the number of superconducting components could make quantum circuits easier to build and allow more material choices.
The results may also advance research into topological superconductors, which resist environmental noise—a major challenge for quantum computing.
Same-spin pairing could stabilize quantum information stored in electron spins, making qubits more reliable.
Towards practical devices
The materials used, iron and magnesium oxide, are already common in technologies like hard drives and magnetic memory. Adding a superconductor could enable hybrid devices combining quantum functionality with existing manufacturing methods.
Although the mechanisms are not yet fully understood, this study opens a new chapter in Josephson junction research. By showing that superconducting synchronization can emerge in unexpected places, scientists may have found a simpler and more versatile path to next-generation quantum computers.
