  Neutral atoms are building blocks of ground-up quantum many-body systems.
Well-controlled and high-fidelity entangling gates are an essential component
for realizing complex neutral atom architectures for quantum computing, quantum
simulation, and measurement with precision better than the standard quantum
limit. In this Letter we report the realization of a M{\o}lmer-S{\o}rensen
unitary between two neutral atoms, based on adiabatic single-photon dressing to
Rydberg levels. We show that this technique is highly robust to noise sources
and experimental imperfections that have limited the fidelity of other
approaches to neutral atom gates.
