# Quantum Fluctuations along Symmetry Crossover in Kondo-correlated Quantum Dot

## TL;DR

This study investigates how quantum fluctuations influence many-body states in a Kondo quantum dot by tuning symmetry with magnetic fields, revealing that noise measurements can quantify fluctuations and their role in quantum phase transitions.

## Contribution

It demonstrates that non-linear noise measurements can directly assess quantum fluctuations during the symmetry crossover in a Kondo quantum dot, linking fluctuations to many-body properties.

## Key findings

- Quantum fluctuations increase along the SU(4) to SU(2) crossover.
- Kondo resonance and electron correlations are enhanced with increased fluctuations.
- Non-linear noise serves as a measure of quantum fluctuations in quantum phase transitions.

## Abstract

Universal properties of entangled many-body states are controlled by their symmetry and quantum fluctuations. By magnetic-field tuning of the spin-orbital degeneracy in a Kondo-correlated quantum dot, we have modified quantum fluctuations to directly measure their influence on the many-body properties along the crossover from $SU(4)$ to $SU(2)$ symmetry of the ground state. High-sensitive current noise measurements combined with the non-equilibrium Fermi liquid theory clarify that the Kondo resonance and electron correlations are enhanced as the fluctuations, measured by the Wilson ratio, increase along the symmetry crossover. Our achievement demonstrates that non-linear noise constitutes a measure of quantum fluctuations that can be used to tackle quantum phase transitions.