  The first generation of multi-qubit quantum technologies will consist of
noisy, intermediate-scale devices for which active error correction remains out
of reach. To exploit such devices, it is thus imperative to use passive error
protection that meets a careful trade-off between noise protection and resource
overhead. Here, we experimentally demonstrate that single-qubit encoding can
significantly enhance the robustness of entanglement and coherence of
four-qubit graph states against local noise with a preferred direction. In
particular, we explicitly show that local encoding provides a significant
practical advantage for phase estimation in noisy environments. This
demonstrates the efficacy of local unitary encoding under realistic conditions,
with potential applications in multi-qubit quantum technologies for metrology,
multi-partite secrecy and error correction.
