Physicists observe optical Magnus effect in single trapped ion

September 13, 2026 at 04:30 PM2 min

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An international team at the Paul Scherrer Institute has experimentally demonstrated the optical Magnus effect for the first time. The effect shifts the point of strongest laser-ion interaction slightly sideways, a finding relevant to precision control of qubits in quantum computers. The results were published in Physical Review Letters.

Key Facts

The optical Magnus effect was experimentally demonstrated for the first time using a single calcium ion held in an ion trap.
The strongest laser-ion interaction occurs not at the beam center but shifted sideways by a few hundred nanometers.
The sideways shift depends only on the laser wavelength, not on how tightly the beam is focused.
The effect could interfere with laser-based qubit control in quantum computers, potentially causing errors.
The forces generated by the effect could be used to couple qubits, enabling more complex computations, according to first author Philip Leindecker.

Optical Magnus Effect

When laser light is focused very tightly, the structure of its electromagnetic field becomes more complicated. As a result, the strongest interaction with an ion does not occur exactly at the beam center but slightly to one side. This small sideways displacement is the optical equivalent of the Magnus effect that curves a spinning table tennis ball. The effect was observed by an international team working at the Paul Scherrer Institute PSI.

Quantum Computing Implications

Lasers are often used to change the states of qubits with very high precision. If the optical Magnus effect is ignored, it could interfere with that control and contribute to errors. The same effect may also be useful: the forces it generates could be used to couple qubits to one another, enabling more complex computations. First author Philip Leindecker from the PSI Center for Photon Science and ETH Zurich explained this potential application.

Single-Ion Measurement

The researchers used a single calcium ion as an extremely sensitive probe, held nearly motionless in an ion trap. They moved the ion through different parts of a tightly focused laser beam and measured how strongly it interacted with the light at each position. This made it possible to measure a shift of just a few hundred nanometers. The measurements also revealed that the size of the sideways shift depends only on the wavelength of the light and not on how tightly the laser beam is focused.