A quantum hybrid of atoms and milligram-scale pendulums: towards gravitational quantum mechanics

Introduction

Does gravity obey the laws of quantum mechanics? Can gravitational fields exist in superposition states or mediate entanglement? These questions lie at the frontier of physics and have crucial implications. Affirmation would constitute a union of the gravitational and quantum realms, while negative results would demand a revision of fundamental physical laws. Only recently have we identified potential paths to entertain experiments to address these questions. Daunting technical challenges nevertheless remain.

Objective

The objective of this proposal is to enable the observation of quantum signatures in gravitational interactions by developing interacting systems of cold atoms and milligram-scale pendulums. This objective will be addressed with three concrete goals:

1. Goal A: Gain unparalleled control over quantum behavior of massive objects by pioneering light-mediated artificial interactions between atoms and milligram-scale masses.
2. Goal B: Observe for the first time the gravitationally driven dynamics of a pair of masses that behave quantum mechanically.
3. Goal C: Demonstrate the basic tenets of entanglement mediated by force fields of macroscopic objects utilizing electrostatic interactions.

Key to Achieving the Objective

The key to achieving the objective is to induce unprecedented levels of quantum delocalization for a massive object. The core novelty of this project is to use an atomic ensemble as a quantum regulator of radiation pressure acting on a massive object.

With interactions of two copies of such a system, the project will set the stage for gravitationally mediated entanglement – an archetypal quantum signature. This approach builds on techniques to control atomic ensembles in optical cavities, where the PI has demonstrated world-leading results.

Though inherently high risk, this proposal lays out a conceivable path toward shedding light on some of the most fundamental questions in contemporary physics.