Realization of a complete Stern-Gerlach interferometer: Towards a test of quantum gravity

TL;DR

This paper reports the first successful realization of a full-loop Stern-Gerlach interferometer using atom chip technology, enabling precise control of magnetic fields to explore quantum mechanics and gravity interface.

Contribution

It demonstrates a fully coherent Stern-Gerlach interferometer with high magnetic field control, addressing previous theoretical challenges and paving the way for fundamental physics tests.

Findings

Achieved a complete Stern-Gerlach interferometer with coherent operation.

Used atom chip technology for precise magnetic field control.

Showed feasibility of future experiments with macroscopic objects doped with a single spin.

Abstract

The Stern-Gerlach effect, discovered a century ago, has become a paradigm of quantum mechanics. Surprisingly there has been little evidence that the original scheme with freely propagating atoms exposed to gradients from macroscopic magnets is a fully coherent quantum process. Specifically, no full-loop Stern-Gerlach interferometer has been realized with the scheme as envisioned decades ago. Furthermore, several theoretical studies have explained why such an interferometer is a formidable challenge. Here we provide a detailed account of the first full-loop Stern-Gerlach interferometer realization, based on highly accurate magnetic fields, originating from an atom chip, that ensure coherent operation within strict constraints described by previous theoretical analyses. Achieving this high level of control over magnetic gradients is expected to facilitate technological as well as fundamental applications, such as probing the interface of quantum mechanics and gravity. While the experimental realization described here is for a single atom, future challenges would benefit from utilizing macroscopic objects doped with a single spin. Specifically, we show that such an experiment is in principle feasible, opening the door to a new era of fundamental probes.