Experimental Evidence of Fractional Entropy in Critical Kondo Systems
Abstract
Unconventional quantum states defying the ubiquitous Fermi-liquid paradigm can emerge in the presence of strong electronic correlations. Among these, non-Abelian anyons - such as Majorana zero modes and Fibonacci anyons - are of particular interest for topological quantum computing due to their non-integer quantum dimensions d>1, which allows for protected non-local encoding and processing of quantum information. However, despite considerable efforts, the unambiguous characterisation of such anyons via transport measurements has proved challenging. Instead, here we provide experimental evidence for the low-temperature fractional entropy Delta S associated with a single anyon, which directly implies its non-Abelian character through the relation Delta S = kB ln(d). This thermodynamic signature is measured in metal-semiconductor quantum circuits engineered to realize quantum-critical states from frustrated interactions. Using a micrometre-scale metallic island coupled to two or three electronic leads, we tune the system to two-channel and three-channel Kondo critical points. By measuring the island charge and exploiting a thermodynamic Maxwell relation, we estimate the entropy associated with the anyons that emerge in these critical states. Our observations reveal fractional values, exposing non-Abelian anyons. The corresponding scaling dimensions are consistent with theoretical predictions for a Majorana zero mode Delta S = kB ln(sqrt(2)) and a Fibonacci anyon Delta S = kB ln(1 +sqrt(5))/2 for two and three channels. These findings establish entropy measurements as a powerful tool for characterizing exotic quantum states.
Related
- Fractional Impurity Entropy from Potential Scattering in a Free Electron Gas
- Entropy-driven transitions between extended integer and fractional quantum Hall regimes
- Planckian dissipation per unit critical entropy as a coupling-free probe of the strange-metal bath
- Spectral Fractional Bosonic Strings: Exact Polyakov Measure and the Critical Dimension
- Universal Driven Critical Dynamics of Entanglement Entropy
BibTeX
@misc{piquard2026experimental,
title = {{Experimental Evidence of Fractional Entropy in Critical Kondo Systems}},
author = {C. Piquard and A. Veillon and Y. Sato and F. Zanichelli and A. Aassime and A. Cavanna and U. Gennser and A. Mitchell and A. Anthore and F. Pierre},
howpublished = {HAL},
year = {2026},
month = nov,
doi = {10.48550/arxiv.2605.00669},
eprint = {2605.00669},
archivePrefix = {arXiv},
url = {https://hal.science/hal-05854188v1},
note = {CC BY-NC-ND},
}
RIS
TY - UNPB
TI - Experimental Evidence of Fractional Entropy in Critical Kondo Systems
AU - C. Piquard
AU - A. Veillon
AU - Y. Sato
AU - F. Zanichelli
AU - A. Aassime
AU - A. Cavanna
AU - U. Gennser
AU - A. Mitchell
AU - A. Anthore
AU - F. Pierre
PY - 2026
DA - 2026/11/05
PB - HAL
DO - 10.48550/arxiv.2605.00669
UR - https://hal.science/hal-05854188v1
AB - Unconventional quantum states defying the ubiquitous Fermi-liquid paradigm can emerge in the presence of strong electronic correlations. Among these, non-Abelian anyons - such as Majorana zero modes and Fibonacci anyons - are of particular interest for topological quantum computing due to their non-integer quantum dimensions d>1, which allows for protected non-local encoding and processing of quantum information. However, despite considerable efforts, the unambiguous characterisation of such anyons via transport measurements has proved challenging. Instead, here we provide experimental evidence for the low-temperature fractional entropy Delta S associated with a single anyon, which directly implies its non-Abelian character through the relation Delta S = kB ln(d). This thermodynamic signature is measured in metal-semiconductor quantum circuits engineered to realize quantum-critical states from frustrated interactions. Using a micrometre-scale metallic island coupled to two or three electronic leads, we tune the system to two-channel and three-channel Kondo critical points. By measuring the island charge and exploiting a thermodynamic Maxwell relation, we estimate the entropy associated with the anyons that emerge in these critical states. Our observations reveal fractional values, exposing non-Abelian anyons. The corresponding scaling dimensions are consistent with theoretical predictions for a Majorana zero mode Delta S = kB ln(sqrt(2)) and a Fibonacci anyon Delta S = kB ln(1 +sqrt(5))/2 for two and three channels. These findings establish entropy measurements as a powerful tool for characterizing exotic quantum states.
ER -