Proposal for a Bell Test with Entangled Atoms of Different Mass

We propose a Bell test experiment using momentum-entangled atom pairs of different masses, specifically metastable helium isotopes 3 H e ∗ and 4 H e ∗ , though the method extends to other atom species. Entanglement is generated via collisions, after which the quantum states are manipulated using two independent atom interferometers, enabling precise phase control over each species. Numerical simulations predict a significant violation of Bell's inequality under realistic conditions. This proposal opens a new paradigm to study the intersection of quantum mechanics and gravity.