The physical implementation of any quantum computer still faces important issues related to scalability and error correction. This study sets up the blueprint for a quantum processor based on molecular spins coupled to superconducting resonators, which control different qudits, read out their final states, and establish coherent communication channels between them. The feasibility of this route is demonstrated by an accurate design of the resonator to reach the strong-coupling regime between a single photon and a single molecule. Very good results for proof-of-principle quantum algorithms and quantum simulations are obtained by numerical simulations of a realistic experimental scenario.
While the recent demonstration of accurate computations of classically intractable simulations on noisy quantum processors brings quantum advantage closer, there is still the challenge of demonstrating it for practical problems. Here we investigate the application of noisy intermediate-scale quantum devices for simulating nuclear magnetic resonance (NMR) experiments in the high-field regime. In this work, the NMR interactions are mapped to a quantum device via a product formula with minimal resource overhead, an approach that we discuss in detail. Using this approach, we show the results of simulations of liquid-state proton NMR spectra on relevant molecules with up to 11 spins, and up to a total of 47 atoms, and compare them with real NMR experiments. Despite current limitations, we show that a similar approach will eventually lead to a case of quantum utility, a scenario where a practically relevant computational problem can be solved by a quantum computer but not by conventional means. We provide an experimental estimation of the amount of quantum resources needed for solving larger instances of the problem with the presented approach. The polynomial scaling we demonstrate on real processors is a foundational step in bringing practical quantum computation closer to reality.
Efficient communication between distant qubits is one of the central challenges in scaling quantum processors. Although engineered spin chain protocols have been extensively investigated theoretically, their experimental realization has remained comparatively limited. Here, we experimentally realize engineered quantum communication protocols through digitally simulated spin Hamiltonian on IonQ's Forte 1/ Forte Enterprise 1 trapped-ion quantum processor. Combining exact numerical simulations with quantum hardware experiments, we benchmark uniform nearest-neighbour and engineered coupling profiles and demonstrate that engineered interactions significantly enhance the fidelity of quantum state transfer. We further show that exploiting the commutation structure of the spin Hamiltonian enables a parallel Trotter decomposition that more faithfully reproduces the target dynamics while substantially reducing the circuit depth and execution time compared to the conventional sequential implementations. Our results demonstrate that programmable quantum processors can effectively realize and efficiently implement quantum communication protocols, bringing Hamiltonian-based quantum communication closer to practical quantum technologies.