Nature Commun. 6, 7503 (2015)

Uniting gravity and quantum mechanics is an ongoing struggle. Experimentally, it involves chasing after the tiniest effects on the most extreme scales. Gravity is suspected of messing with quantum mechanics by introducing small modifications to the commutator relations, but we do not yet have any proof that that is indeed the case. Still, modified commutators could potentially be revealed in low-energy mechanical oscillators, which makes them a good place to look for clues.

Mateusz Bawaj and colleagues analysed several micro- and nano-oscillators to explore the bounds on modifications to the commutator relations between their position and momentum operators. They used oscillators with high quality-factors and low background noise with different geometries and masses distributed around the Planck mass, including a 33 mg double-paddle oscillator, a 20 μg silicon wheel oscillator and a 20 ng membrane. Bawaj et al. lowered the known limits by several orders of magnitude, but we have yet to catch gravity red handed.