Spectral fluctuation and $\frac{1}{f^{\alpha}}$ noise in the energy level statistics of interacting trapped bosons

TL;DR

This paper investigates spectral fluctuations in interacting trapped bosons, revealing a transition from collective to single-particle behavior and demonstrating the ubiquity of 1/f^α noise in quantum systems with complex interactions.

Contribution

It provides a detailed analysis of spectral fluctuation transitions in trapped bosons, highlighting deviations from classical random matrix predictions and the presence of 1/f^α noise.

Findings

Low-lying levels show quasi-degenerate states with Shnirelman peaks.

Transition from Poisson to Wigner distribution with increasing particle number.

High-lying levels exhibit uncorrelated Poisson statistics.

Abstract

It has been recently shown numerically that the transition from integrability to chaos in quantum systems and the corresponding spectral fluctuations are characterized by $\frac{1}{f^{\alpha}}$ noise with $1\leq\alpha\leq 2$. The system of interacting trapped bosons is inhomogeneous and a complex system. The presence of external harmonic trap makes it more interesting as in the atomic trap the bosons occupy partly degenerate single-particle states. Earlier theoretical and experimental results show that at zero temperature the low-lying levels are of collective nature and high-lying excitations are of single particle nature. We observe that for few bosons, $P(s)$ distribution shows the Shnirelman peak which exhibits a large number of quasi-degenerate states. For large number of bosons the low-lying levels are strongly affected by the interatomic interaction and the corresponding level fluctuation shows a transition to Wigner with increase in particle number. It does not follow GOE (Gaussian Orthogonal Ensemble) Random Matrix predictions. For high-lying levels we observe the uncorrelated Poisson distribution. Thus it may be a very realistic system to prove that $\frac{1}{f^{\alpha}}$ noise is ubiquitous in nature.