Magnetic Vortex Becomes a Quantum Bit express
Magnetic vortices in superconductors, like whirlpools in water, typically scatter energy and quickly vanish due to internal friction — dissipation. This hampers their use in quantum chips. But in a film of tiny aluminum grains, a vortex gets trapped and resembles a whirlpool in a narrow well: it spins either one way or the other. Quantum nature allows it to spin both ways at once until measured. This double life lasts for milliseconds — an eternity in the micro-world. Scientists have learned to flip the vortices with microwave pulses (spectroscopy) and read out their state without loss. Each vortex carries exactly one quantum of magnetic flux — a billionth of Earth's field. The idea of Alexei Kitaev to use such structures for noise-tolerant quantum computing has been directly confirmed.
Original abstract
as written by the authors arXiv:2510.19769
Abrikosov vortices, where the superconducting gap is completely suppressed in the core, are dissipative, semi-classical entities that impact applications from high-current-density wires to superconducting quantum devices. In contrast, we present evidence that vortices trapped in granular superconducting films can behave as two-level systems, exhibiting microsecond-range quantum coherence and energy relaxation times that reach fractions of a millisecond. These findings support recent theoretical modeling of superconductors with granularity on the scale of the coherence length as tunnel junction networks, resulting in gapped vortices. Using the tools of circuit quantum electrodynamics, we perform coherent manipulation and quantum non-demolition readout of vortex states in granular aluminum microwave resonators, heralding new directions for quantum information processing, materials characterization, and sensing.
Each such vortex carries just one quantum of magnetic flux — about a billionth of Earth's magnetic field.