Tabletop quantum gravity
Gravitationally-induced entanglement between two masses held in spatial superposition
An interactive model of the QGEM / BMV tabletop proposal for detecting gravitationally-induced entanglement — built to make the phase formula and the quantized-vs-semiclassical gravity debate tangible, not just abstract.
All parameter ranges and presets are drawn from published proposals; the 3D visualization and sound are illustrative, not a substitute for the real experiment's noise budget.
Each mass is placed in a spatial superposition of two locations using a Stern–Gerlach–type interferometer.
The two interferometers are held side by side, close enough that their gravitational fields overlap.
Gravity alone mediates a phase between the branches — no other force is permitted to pass between the masses.
The interferometers close and an entanglement witness is measured. A violation would mean gravity carried quantum information.
This uses the same scaling as the original QGEM proposal, simplified for a live readout — it isn't a substitute for the full noise budget (electromagnetic screening, graviton-exchange corrections, vibration isolation) that a real proposal has to clear. A phase of order φ ≈ 1 is the rough benchmark the literature treats as sufficient for a detectable witness violation, which is what the threshold marker above represents.
Nobody has run this experiment yet. Current designs sit right at the edge of achievable mass, separation, and coherence time — this simulator's slider ranges are drawn from real proposed regimes (femtogram-scale masses, tens to hundreds of microns, up to a few seconds of coherence), not arbitrary numbers.
Switch the gravity model to semiclassical and no entanglement forms, no matter how high φ climbs. Some classical models of gravity (Newton–Schrödinger–type) predict exactly that — which is the whole reason this experiment could distinguish quantum from classical gravity, and, one level up, bears on the split between interpretations like Everett's many-worlds and Penrose's objective reduction.