Testing Gravity's Quantum Nature with Spin ⚡ экспресс
Previously, gravitationally induced entanglement has been proposed as a way to test the nonclassicality of gravity in tabletop experiments, but was limited to the Newtonian regime. This work investigates entanglement generated by the frame-dragging effect. It calculates the entanglement phase between the rotational degrees of freedom of a massive source and the trajectories of a test particle in an interferometer. Two approaches are used: Schrödinger evolution with a quantized Lense–Thirring Hamiltonian in the large angular momentum limit, and an on-shell action calculation of linear quantum gravity in the stationary phase approximation. Both methods yield the same phase, matching the proper time difference between the interferometer arms. The path integral further shows how gravitational retardation modifies the phase, making the description explicitly local and relativistically causal. Under standard assumptions about locality and mediators, the detected entanglement would indicate the nonclassical nature of the gravitational interaction.
Einstein's theory says: a rotating massive body drags space along with it, like a spoon pulling through thick honey. This phenomenon is called frame-dragging, and it's especially pronounced around black holes and neutron stars. But a faint trace exists even in objects on a lab bench.
In a new experiment, a microparticle will fly past a heavy rotating sphere along two different paths. Because the "honey" flows at slightly different speeds on each lane, time ticks unevenly for the particle. The difference is a tiny fraction of an atom's jitter, but that's enough to entangle the paths at the quantum level. At the meeting point, the particle will reveal itself as having traveled both routes at once, and the detector will record it.
If it works, this will be the first demonstration that gravity plays by quantum rules. Physics today is fractured: relativity describes stars, quantum mechanics describes atoms, and together they don't mesh. This tabletop experiment would be a bridge to a unified picture, linking black holes with the first moments of spacetime curvature after the Big Bang.
🎯 Earth's rotation also drags space: in 2011, the Gravity Probe B satellites confirmed that our planet twists spacetime around itself, shifting gyroscopes by 37 milliarcseconds per year.
🎬 Quantum gravity inspires sci-fi writers to imagine devices that manipulate spacetime—from warp drives to gravity suits.