Long-distance entanglement and quantum teleportation in XX spin chains

TL;DR

This paper analyzes XX spin chains to understand their capacity for long-distance entanglement and quantum teleportation, revealing that certain chain configurations enable high-fidelity teleportation over long distances.

Contribution

It introduces and compares two models of XX spin chains, deriving exact correlations and demonstrating their potential for long-distance quantum teleportation.

Findings

Model I supports true long-distance entanglement at zero temperature.

Model II supports quasi long-distance entanglement that decreases slowly with chain length.

Model II enables efficient high-fidelity qubit teleportation in long chains at moderate temperatures.

Abstract

Isotropic XX models of one-dimensional spin-1/2 chains are investigated with the aim to elucidate the formal structure and the physical properties that allow these systems to act as channels for long-distance, high-fidelity quantum teleportation. We introduce two types of models: I) open, dimerized XX chains, and II) open XX chains with small end bonds. For both models we obtain the exact expressions for the end-to-end correlations and the scaling of the energy gap with the length of the chain. We determine the end-to-end concurrence and show that model I) supports true long-distance entanglement at zero temperature, while model II) supports {\it ``quasi long-distance''} entanglement that slowly falls off with the size of the chain. Due to the different scalings of the gaps, respectively exponential for model I) and algebraic in model II), we demonstrate that the latter allows for efficient qubit teleportation with high fidelity in sufficiently long chains even at moderately low temperatures.