# Quantum state transfer in a XX chain with impurities

## TL;DR

This paper studies how impurities in a quantum XX spin chain affect the localization and entanglement of single excitation states, revealing conditions for high-fidelity quantum state transfer.

## Contribution

It introduces a method to control localization and entanglement in an XX chain with impurities, optimizing quantum state transfer fidelity.

## Key findings

- Control of localized and extended states via impurity coupling strength
- Identification of regimes with high-fidelity quantum state transmission
- Short transmission time proportional to half the chain length

## Abstract

One spin excitation states are involved in the transmission of quantum states and entanglement through a quantum spin chain, the localization properties of these states are crucial to achieve the transfer of information from one extreme of the chain to the other. We investigate the bipartite entanglement and localization of the one excitation states in a quantum $XX$ chain with one impurity. The bipartite entanglement is obtained using the Concurrence and the localization is analyzed using the inverse participation ratio. Changing the strength of the exchange coupling of the impurity allows us to control the number of localized or extended states. The analysis of the inverse participation ratio allows us to identify scenarios where the transmission of quantum states or entanglement can be achieved with a high degree of fidelity. In particular we identify a regime where the transmission of quantum states between the extremes of the chain is executed in a short transmission time $\sim N/2$, where $N$ is the number of spins in the chain, and with a large fidelity.