Heavy balls on a trampoline bend the fabric, and their dents intertwine paths. Similarly, gravity: two massive particles curve space and feel each other's influence. Scientists built a setup where particles, guided by quantum signals, travel along two paths at once. When they meet, they don't just collide: their gravitational interaction entangles their quantum states: the particles become a single entity, even if separated far apart. Surprisingly, the strength of this connection doesn't depend on mass. A dust speck, a virus crumb — the effect is unchanged. This contradicts the usual rule 'the heavier, the stronger the pull,' but here a balance of quantum and gravitational forces is at play.
Due to mutual attraction, the paths never converge perfectly, but this imprecision outlines the bounds of suitable masses: light particles won't notice each other, heavy ones will destroy the quantum effect. Real disturbances (thermal jitter, scattering) only narrow the corridor. A concrete embodiment: diamond dust grains levitated in a magnetic field. Diamond is carbon, and its vacancy defects act as quantum pushers.
Quantum objects never stand still: even in absolute vacuum and at zero temperature, they always tremble slightly. This jitter is a fundamental limit for instrument precision.