AMO
In the literature: open
Atom interferometry determination of G at 10 ppm
In plain words
Atoms in free fall make test masses that cannot twist, stretch or be magnetized like a pendulum fiber, so they could give G free of the usual suspects. Their best result so far is about ten times less precise than needed.
Precise statement
Atom-interferometric gravity gradiometry with well-characterized source masses gave G with about 150 ppm uncertainty (Rosi et al 2014). Determine G with uncertainty below 1e-5 relative by a cold-atom method, sufficient to discriminate among the discrepant macroscopic results.
What would settle it
A cold-atom G measurement with total uncertainty below 10 ppm and a published complete error budget.