Spin Chain Quantum Communication on a Trapped-Ion Processor

As quantum processors scale, transporting quantum information between distant qubits becomes a major bottleneck. Traditional methods, such as sequential SWAP gates, introduce significant overhead in circuit depth and error accumulation. This paper investigates whether engineered spin chain protocols—which use the natural many-body dynamics of coupled spins—can serve as a more efficient quantum data bus on programmable trapped-ion hardware.

The researchers utilized IonQ’s Forte and Forte Enterprise trapped-ion processors to simulate the XY spin Hamiltonian. They compared two coupling strategies: uniform nearest-neighbor (NN) couplings and engineered couplings designed for Perfect State Transfer (PST). To implement these continuous-time dynamics on a gate-based processor, they employed a first-order Trotter decomposition. Additionally, they introduced a parallel Trotterization technique that groups commuting interaction terms into simultaneous layers, thereby reducing the total circuit depth and execution time.

The experiments confirmed that engineered coupling profiles significantly enhance state-transfer fidelity compared to uniform chains. The parallel Trotter decomposition was shown to be superior to the conventional sequential approach; it not only reduced the circuit depth but also more faithfully reproduced the target Hamiltonian dynamics. The results demonstrate that programmable trapped-ion processors can effectively synthesize complex spin Hamiltonians, providing a viable path toward scalable, Hamiltonian-based quantum communication.

This work bridges the gap between theoretical proposals for spin-chain quantum communication and practical implementation on current quantum hardware. By demonstrating that Hamiltonian engineering and parallel circuit optimization can mitigate communication overheads, the study provides a scalable framework for moving quantum information across large-scale processors without relying solely on long sequences of local SWAP gates.