Symmetry deduction from spectral fluctuations in complex quantum systems

TL;DR

This paper demonstrates that in chaotic quantum systems, spectral fluctuation and symmetry properties can be inferred directly from higher-order spectral statistics without the need for desymmetrization, across various physical systems.

Contribution

It introduces a method to deduce symmetry structures from spectral fluctuations using higher-order statistics, bypassing the traditional desymmetrization process.

Findings

Higher-order spectral statistics reveal symmetry information.

The k-th order spacing ratio distribution matches a modified Dyson index.

Validated across random matrices, quantum billiards, spin chains, and nuclear resonances.

Abstract

The spectral fluctuations of complex quantum systems, in appropriate limit, are known to be consistent with that obtained from random matrices. However, this relation between the spectral fluctuations of physical systems and random matrices is valid only if the spectra are desymmetrized. This implies that the fluctuation properties of the spectra are affected by the discrete symmetries of the system. In this work, it is shown that in the chaotic limit the fluctuation characteristics and symmetry structure for any arbitrary sequence of measured or computed levels can be inferred from its higher-order spectral statistics without desymmetrization. In particular, we consider a spectrum composed of $k>0$ independent level sequences with each sequence having the same level density. The $k$-th order spacing ratio distribution of such a composite spectrum is identical to its nearest neighbor counterpart with modified Dyson index $k$. This is demonstrated for the spectra obtained from random matrices, quantum billiards, spin chains and experimentally measured nuclear resonances with disparate symmetry features.