Entanglement of magnetically levitated massive Schrödinger cat states by induced dipole interaction

Quantum entanglement provides a novel way to test short-distance quantum physics in a nonrelativistic regime. We provide entanglement-based protocols to potentially test the magnetically induced dipole-dipole interaction and the Casimir-Polder potential between the two nanocrystals kept in a Schrödinger cat state. Our scheme is based on the Stern-Gerlach (SG) apparatus, where we can witness the entanglement mediated by these interactions for the nanocrystal mass m∼10-19 kg with a spatial superposition size of order 0.1μm in a trap relying on diamagnetic levitation. We show that it is possible to close the SG interferometer in position and momentum with a modest gradient in the magnetic field.