Stern-Gerlach Interferometry with the Atom Chip

TL;DR

This review discusses a decade of Stern-Gerlach interferometry on the atom chip, highlighting novel configurations, coherence achievements, and potential applications in quantum foundations, metrology, and surface probing.

Contribution

It reports the first realization of a full-loop Stern-Gerlach interferometer with atom chips, demonstrating high magnetic field control for coherent quantum experiments.

Findings

First observation of Stern-Gerlach spatial interference fringes

First full-loop Stern-Gerlach interferometer realization

High-precision magnetic field control enabling coherence

Abstract

In this invited review in honor of 100 years since the Stern-Gerlach (SG) experiments, we describe a decade of SG interferometry on the atom chip. The SG effect has been a paradigm of quantum mechanics throughout the last century, but there has been surprisingly 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 SG interferometer (SGI) has been realized with the scheme as envisioned decades ago. Furthermore, several theoretical studies have explained why it is a formidable challenge. Here we provide a review of our SG experiments over the last decade. We describe several novel configurations such as that giving rise to the first SG spatial interference fringes, and the first full-loop SGI realization. These devices are 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 applications such as probing of surfaces and currents, as well as metrology. Fundamental applications include the probing of the foundations of quantum theory, gravity, and the interface of quantum mechanics and gravity. We end with an outlook describing possible future experiments.