Spin chains for robust state transfer: Modified boundary couplings vs. completely engineered chains

TL;DR

This paper compares the robustness of quantum state transfer in engineered and boundary-controlled spin chains under static noise, highlighting that boundary control can achieve high fidelity without extensive engineering.

Contribution

It demonstrates that boundary-controlled chains can match or surpass engineered chains in robustness against noise, reducing the need for complex coupling engineering.

Findings

Boundary-controlled chains can achieve high fidelity transfer without extensive engineering.

Transfer efficiency depends on fidelity and transfer time considerations.

Boundary control offers a practical alternative to fully engineered chains in noisy environments.

Abstract

Quantum state transfer in the presence of noise is one of the main challenges in building quantum computers. We compare the quantum state transfer properties for two classes of qubit chains under the influence of static randomness. In fully engineered chains all nearest-neighbor couplings are tuned in such a way that a single-qubit state can be transferred perfectly between the ends of the chain, while in boundary-controlled chains only the two couplings between the transmitting and receiving qubits and the remainder of the chain can be optimized. We study how the noise in the couplings affects the state transfer fidelity depending on the noise model and strength as well as the chain type and length. We show that the desired level of fidelity and transfer time are important factors in designing a chain. In particular we demonstrate that transfer efficiency comparable or better than that of the most robust engineered systems can also be reached in boundary-controlled chains without the demanding engineering of a large number of couplings.