Quantum state transfer in a XX chain with impurities
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.