Parrondo-type enhancement of quantum-state transfer in spin chains

TL;DR

This paper demonstrates that periodic switching between two Hamiltonians in spin chains, inspired by Parrondo's paradox, can enhance quantum-state transfer fidelity beyond static configurations, leveraging coherent interference effects.

Contribution

It introduces a novel Floquet-based control protocol using Hamiltonian switching to improve quantum-state transfer in spin chains, inspired by Parrondo's paradox.

Findings

Periodic driving outperforms static configurations in fidelity

Enhancement due to noncommutativity and interference effects

Protocol remains robust under moderate disorder

Abstract

Spin chains have been widely studied as quantum channels for short-distance communication in quantum devices, where many-body dynamics can mediate quantum-state transfer between distant sites. In finite unmodulated chains, however, dispersion and interference effects associated with the static Hamiltonian often limit the achievable transfer fidelity. Here we investigate the transfer of single-qubit and Bell states in finite $XX$ spin chains under periodic switching between two Hamiltonians with different boundary couplings. Inspired by Parrondo's paradox, we examine whether alternating between two configurations that individually yield suboptimal transfer fidelities can generate enhanced coherent transmission. Using Floquet theory together with numerical simulations in the single-excitation subspace, we show that periodic driving can outperform static configurations and achieve higher transfer fidelities. This enhancement originates from the noncommutativity of the driven Hamiltonians and reflects a purely coherent interference effect. We further analyze the dependence of the protocol on system size and driving parameters and examine its robustness to asymmetric boundary couplings. Our results show that the transfer fidelity remains stable under moderate disorder, indicating that simple time-dependent control of boundary couplings provides an effective strategy to enhance quantum-state transfer in spin-chain communication channels and optimize quantum information processing in engineered many-body systems.