Diamagnetic micro-chip traps for levitated nanoparticle entanglement experiments

• DOI: 10.48550/arxiv.2411.02325
• Publication Date: 2024-01-01
• Authors: Elahi, Shafaq Gulzar; Schut, Martine; Dana, Andrew; Grinin, Alexey; Bose, Sougato; Mazumdar, Anupam; Geraci, Andrew
• Keywords: Quantum Physics; High Energy Physics - Phenomenology; High Energy Physics - Phenomenology (hep-ph); FOS: Physical sciences; Quantum Physics (quant-ph)

11 pages, 8 figures<br/>The Quantum Gravity Mediated Entanglement (QGEM) protocol offers a novel method to probe the quantumness of gravitational interactions at non-relativistic scales. This protocol leverages the Stern-Gerlach effect to create $\mathcal{O}(\sim μm)$ spatial superpositions of two nanodiamonds (mass $\sim 10^{-15}$ kg) with NV spins, which are then allowed to interact and become entangled solely through the gravitational interaction. Since electromagnetic interactions such as Casimir-Polder and dipole-dipole interactions dominate at this scale, screening them to ensure the masses interact exclusively via gravity is crucial. In this paper, we propose using magnetic traps based on micro-fabricated wires, which provide strong gradients with relatively modest magnetic fields to trap nanoparticles for interferometric entanglement experiments. The design consists of a small trap to cool the center-of-mass motion of the nanodiamonds and a long trap with a weak direction suitable for creating macroscopic superpositions. In contrast to permanent-magnet-based long traps, the micro-fabricated wire-based approach allows fast switching of the magnetic trapping and state manipulation potentials and permits integrated superconducting shielding, which can screen both electrostatic and magnetic interactions between nanodiamonds in a gravitational entanglement experiment. The setup also provides a possible platform for other tests of quantum coherence in macroscopic systems and searches for novel short-range forces.<br/>