Researchers report experimental evidence that tiny, exotic particles called non‑Abelian anyons appear in engineered quantum circuits. They measured a small, fractional change of entropy at very low temperature. This fraction matches the theoretical signature expected for two well‑known anyon types: a Majorana mode and a Fibonacci anyon.

The team built metal–semiconductor devices with a micrometre‑scale metallic island connected to electronic leads through adjustable constrictions called quantum point contacts (QPCs). By tuning the transmissions of two or three QPCs they drove the system to two‑channel and three‑channel Kondo critical points. The Kondo effect here is a competition between multiple electronic “baths” that try to screen a single effective impurity. The experiment measured the island’s mean charge with a nearby capacitive sensor and used a thermodynamic Maxwell relation (a way to relate measured charge changes to entropy) to extract the change in entropy associated with the impurity.

Fractional entropy is important because it ties directly to the anyon’s quantum dimension d through the relation ΔS = kB ln(d), where kB is Boltzmann’s constant. For non‑Abelian anyons this dimension is non‑integer. The measured impurity entropy values are fractional and are, within experimental accuracy, consistent with the predicted values for a Majorana zero mode in the two‑channel case (ΔS = kB ln(√2)) and for a Fibonacci anyon in the three‑channel case (ΔS = kB ln(ϕ), with ϕ the golden ratio). The authors say they bounded the impurity entropy from above and below during the crossover into and away from the critical points, supporting the conclusion that the entropy is non‑integer.

This approach matters because it uses a direct thermodynamic signature rather than only transport (current or conductance) measurements. Measuring impurity entropy circumvents some problems of tiny bulk signatures and does not presuppose a microscopic model: a measured fractional ΔS = kB ln(d) is an unbiased indication of non‑Abelian statistics. The work also shows that carefully engineered multi‑channel Kondo circuits can be a controlled platform to explore non‑Fermi‑liquid physics and emergent anyonic excitations.