Picture heavy balls resting on a stretchy trampoline: each one sinks into the fabric, and their dents overlap, causing the balls to roll toward each other. This analogy helps explain how gravity — the curvature of spacetime — links massive particles. But what if you bring gravity and quantum mechanics together? Scientists have devised a thought experiment where particles, steered by quantum signals, move along two paths at once — much like a wave passing through two slits simultaneously. When their trajectories cross, something more than a collision happens: gravitational interaction entangles their quantum states. Entanglement is a special connection in which particles form a single system, and measuring one instantly determines the state of the other, no matter how far apart they are. Strikingly, the strength of this gravitational entanglement does not depend on the mass of the participants. Whether it's a dust grain or an object the size of a virus, the effect remains unchanged. This contradicts the familiar rule "the heavier, the stronger the attraction," but here a balance of quantum and gravitational forces comes into play: quantum effects tend to smear particles across trajectories, while gravity pulls them together, and the resulting entanglement turns out to be a universal constant.

Because of mutual gravitational attraction, the paths of the particles never converge perfectly — there is always a microscopic imprecision. This imprecision outlines the boundaries of viable masses: particles that are too light cannot gravitationally "feel" each other, and no entanglement arises; particles that are too heavy will destroy the fragile quantum superposition, collapsing it into an ordinary classical state. Real-world disturbances — thermal jitter of atoms, scattering off residual gases — only narrow this mass corridor, but do not change the essence. A concrete realization of the idea is an experiment with diamond dust levitating in a magnetic field. Diamond is carbon with a rigid crystal lattice, and its vacancy defects (nitrogen atoms replacing carbon) serve as quantum "pushers": their spin states control the motion of the dust grains, allowing the trajectories to be separated and brought together.