# Quantum information measures of the Aharonov-Bohm ring in uniform magnetic fields

## TL;DR

This paper investigates quantum information measures such as Shannon entropy, Fisher information, and Onicescu energy in a 2D nanoring under combined magnetic and Aharonov-Bohm flux fields, revealing their dependence on field strength and geometry.

## Contribution

It provides analytical expressions and insights into how quantum information measures vary with magnetic field, flux, and geometry in a nanoring, including their relation to persistent currents.

## Key findings

- Sum of position and momentum Shannon entropies is field-independent.
- Products of Fisher information and Onicescu energies are B-independent.
- Variation of entropy or Onicescu energy with AB flux determines persistent current.

## Abstract

Shannon quantum information entropies $S_{\rho,\gamma}$, Fisher informations $I_{\rho,\gamma}$, Onicescu energies $O_{\rho,\gamma}$ and complexities $e^SO$ are calculated both in position (subscript $\rho$) and momentum ($\gamma$) spaces for azimuthally symmetric 2D nanoring that is placed into combination of transverse uniform magnetic field $\bf B$ and Aharonov-Bohm (AB) flux $\phi_{AB}$ and whose potential profile is modeled by superposition of quadratic and inverse quadratic dependencies on radius $r$. Increasing intensity $B$ flattens momentum waveforms $\Phi_{nm}({\bf k})$ and in the limit of infinitely large fields they turn to zero, what means that the position wave functions $\Psi_{nm}({\bf r})$, which are their Fourier counterparts, tend in this limit to the $\delta$-functions. Position (momentum) Shannon entropy depends on the field $B$ as a negative (positive) logarithm of $\omega_{eff}\equiv\left(\omega_0^2+\omega_c^2/4\right)^{1/2}$, where $\omega_0$ determines the quadratic steepness of the confining potential and $\omega_c$ is a cyclotron frequency. This makes the sum ${S_\rho}_{nm}+{S_\gamma}_{nm}$ a field-independent quantity that increases with the principal $n$ and azimuthal $m$ quantum numbers and does satisfy entropic uncertainty relation. Position Fisher information does not depend on $m$, linearly increases with $n$ and varies as $\omega_{eff}$ whereas its $n$ and $m$ dependent Onicescu counterpart ${O_\rho}_{nm}$ changes as $\omega_{eff}^{-1}$. The products ${I_\rho}_{nm}{I_\gamma}_{nm}$ and ${O_\rho}_{nm}{O_\gamma}_{nm}$ are $B$-independent quantities. A dependence of the measures on the ring geometry is discussed. It is argued that a variation of the position Shannon entropy or Onicescu energy with the AB field uniquely determines an associated persistent current as a function of $\phi_{AB}$ at $B=0$. An inverse statement is correct too.