Mass-independent scheme for enhancing spatial quantum superpositions
Run Zhou, Ryan J. Marshman, Sougato Bose, Anupam Mazumdar
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 $[O(10--100)\phantom{\rule{4pt}{0ex}}\textmu{}\mathrm{m}]$ of mesoscopic masses $[m\ensuremath{\sim}O({10}^{\ensuremath{-}14}--{10}^{\ensuremath{-}15})\phantom{\rule{0.16em}{0ex}}\mathrm{kg}]$ 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 wave-packet expansions or quantum ancilla- (for example, spin-) dependent forces, all of whose efficacy reduces with mass. Thus increasing the spatial splitting independently 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 analyze an example system which uses the Stern-Gerlach effect to creating a small initial splitting and then apply our diamagnetic repulsion method to enhance the superposition size $O(400--600)\phantom{\rule{4pt}{0ex}}\textmu{}\mathrm{m}$ from an initial modest split of the wave function. We provide an analytical and numerical analysis of our scheme.