Heisenberg Spin Bus as a Robust Transmission Line for Perfect State Transfer

TL;DR

This paper demonstrates that a strongly coupled antiferromagnetic spin chain can serve as a robust quantum communication channel for perfect state transfer, with the process resilient to coupling variations and optimized by quantum interference effects.

Contribution

It introduces a perturbative approach to achieve perfect state transfer in spin buses, highlighting robustness and interference effects that optimize transfer times.

Findings

Perfect state transfer is achievable with second order perturbation.

PST robustness against coupling variations is confirmed.

Optimal transfer times decrease with larger qubit separations.

Abstract

We study the protocol known as quantum state transfer for a strongly coupled antiferromagnetic spin chain or ring (acting as a spin bus), with weakly coupled external qubits. By treating the weak coupling as a perturbation, we find that perfect state transfer (PST) is possible when second order terms are included in the expansion. We also show that PST is robust against variations in the couplings along the spin bus and between the bus and the qubits. As evidence of the quantum interference which mediates PST, we show that the optimal time for PST can be smaller with larger qubit separations, for an even-size chain or ring.