Macroscopic Matter Wave Interferometry

Researchers are close to producing quantum superpositions of objects measuring from nanometers to micrometers, and matter-wave interferometry is the leading technique for pushing quantum behavior into larger systems. That push is also a theoretical challenge. Physicists must design new interferometers, locate the sources of noise and decoherence, understand how an object's size affects its behavior, and consider whether quantum theory itself needs adjusting at these scales.

This work lays out the theory behind recent progress in interferometry with molecules and nanoparticles. It also proposes a physical, objective way to measure how macroscopic an experiment is, placing such experiments alongside other macroscopic quantum superposition phenomena for comparison.