Weak Attraction: How Gravity Spares Quantum Superpositions ⚡ экспресс
Using the closed-time-path integral method, an influence functional was obtained describing gravitationally induced decoherence of a massive system in a spatial superposition, interacting with an ambient scalar field and linearized gravity. In the non-relativistic quasi-static limit, the decoherence exponent is expressed through a bilinear form of the difference of the system's stress-energy tensors and an effective noise kernel containing graviton propagators. For Newtonian long-range interaction and a dilute gas of finite wave packets with spacetime coarse-graining, analytical expressions were derived. It is shown that the dominant contribution accumulates logarithmically over a wide range of distances, remaining under realistic conditions small compared to decoherence from collisions.
A single particle can be in two places at once — that's superposition. But any interaction, like a shout, instantly 'collapses' this uncertainty. It was long thought that even gravity could interfere. Following the ideas of Roger Penrose and John Wheeler, physicists have finally rigorously described the effect: gravity itself destroys superposition. But how weakly!
Ordinary collisions with air molecules for a quantum state are like the clang of a blacksmith's hammer. Gravity, on the other hand, is a barely perceptible whisper in a quiet room. To hear it, almost perfect isolation is needed. And here's the main surprise: this whisper grows with distance surprisingly lazily. For instance, by expanding a superposition from a meter to a kilometer, you amplify the gravitational noise only a few times, not a thousand. The accumulated effect is almost indistinguishable — like an echo that, as it spreads, barely changes its intensity.
This sets a fundamental limit for quantum technologies. Someday, ultra-precise detectors hunting for gravitational waves will hit this barely noticeable rumble. And then the quietest sound of nature will become the only thing hindering us. The irony is that the weakest of all forces will turn out to be an insurmountable wall.
🎯 The gravitational influence on superposition grows astonishingly slowly with distance: the first kilometer adds as much as the first meter.
🎬 In science fiction, gravity is often portrayed as a force that 'collapses' quantum probabilities into one reality — as if the Universe makes a choice.