High-fidelity multiqubit Rydberg gates via two-photon adiabatic rapid passage

We present a robust protocol for implementing high-fidelity multiqubit controlled phase gates (C ^k Z) on neutral atom qubits coupled to highly excited Rydberg states. Our approach is based on extending adiabatic rapid passage to two-photon excitation via a short-lived intermediate excited state common to alkali-atom Rydberg experiments, accounting for the full impact of spontaneous decay and differential AC Stark shifts from the complete manifold of hyperfine excited states. We evaluate and optimise gate performance, concluding that for Cs and currently available laser frequencies and powers, a CCZ gate with fidelity \mathcal{F} > 0.995$ for three qubits and CCCZ with \mathcal{F} > 0.99$ for four qubits is attainable in \sim 1.8$ μs via this protocol. Higher fidelities are accessible with future technologies, and our results highlight the utility of neutral atom arrays for the native implementation of multiqubit unitaries.