Quantum tools for classical sensing: Moiré fringes of megadalton clusters as a force probe

Quantum theory doesn’t have strict size limits. Yet, apples, pebbles, and people don’t exist in superposition. Pedalino et al. sought to test the limit for how large and complex objects could be, while still showing quantum interference patterns.

To do this, they built a robust new matter-wave interferometer platform — the multi-scale cluster interferometer experiment (MUSCLE). By sending a neutral beam of sodium clusters through three deep-UV light gratings to a mass-selective detector, the team could measure either quantum interference patterns or classical moiré shadow patterns.

As the sodium clusters become more massive, their de Broglie wavelength becomes so short that quantum wave behavior effectively turns into ray-like behavior, in line with the correspondence principle of quantum mechanics. In this regime, the observed fringe pattern can be read either as quantum interference or as a classical moiré shadow, and the two become experimentally indistinguishable.

Applying external electric or magnetic fields can shift the fringes, allowing the team to infer the electric and magnetic moments or optical polarizabilities of the clusters.

“We can detect shifts on the order of a nanometer,” said author Sebastian Pedalino. “That’s what gives us the very high force sensitivity, potentially down to 10⁻³³ newtons.”

The team aims to slow down the speed at which particles pass through the interferometer. This will increase the de Broglie wavelength, creating the conditions needed to try to observe genuine quantum interference and demonstrate quantum superposition.

“On the fundamental side, we are gradually closing the gap between microscopic quantum experiments and the scales of real-world devices and complex nanostructures,” said Pedalino. “The interferometer is ready for megadalton particles. Now, we have to work on slowing the beam to bring these heavy clusters fully into the quantum regime.”

Source: “de Broglie and moiré metrology: From atoms to massive metal clusters,” by Sebastian Pedalino, Richard Ferstl, Bruno E. Ramírez-Galindo, Severin Sindelar, Stefan Gerlich, and Markus Arndt, AVS Quantum Science (2025). The article can be accessed at https://doi.org/10.1116/5.0301389 .

This paper is part of the Advances in Matter Wave Optics Collection, learn more here .