Mass-independent scheme for enhancing spatial quantum superpositions

Abstract

Placing a large mass in a large spatial superposition, such as a Schr\"odinger Cat state is a significant and important challenge. In particular, the large spatial superposition (${\cal O}(10-100)$ $\mu$m) of mesoscopic masses ($m\sim {\cal O}(10^{-14} -10^{-15})$ kg) makes it possible to test the quantum nature of gravity via entanglement in the laboratory. To date, the proposed methods of achieving this spatial delocalization are to use wavepacket expansions or quantum ancilla (for example spin) dependent forces, all of whose efficacy reduces with mass. Thus increasing the spatial splitting independent of the mass is an important open challenge. In this paper, we present a method of achieving a mass-independent enhancement of superposition via diamagnetic repulsion from current-carrying wires. We analyse an example system which uses the Stern-Gerlach effect to creating a small initial splitting, and then apply the diamagnetic repulsion method to enhance the superposition size ${\cal O}(400-600)$ $\mu$m from an initial modest split of the wavefunction. We provide an analytic and numeric analysis of our scheme.