Breakthrough laser technique holds quantum matter in stable packets

 

For the first time, physicists have generated and observed stable bright matter-wave solitons with attractive interactions within a grid of laser light.

In the quantum world, atoms usually travel as waves that spread out, but solitons stay concentrated in one spot. They have been created before in open space, but this is the first time they have been stabilized inside a repeating laser structure using attractive forces. This development gives scientists a new way to hold and guide clusters of atoms, a key requirement for developing future quantum technologies.

The research is published in a paper in Physical Review Letters.

To create these solitons, the researchers used a cloud of cesium atoms cooled to temperatures near absolute zero (a Bose–Einstein condensate). They placed the atoms in an optical lattice that they created with lasers. This grid of light acted as a container, holding the atoms in specific, repeating positions. The researchers then used magnetic fields to make the atoms attract one another, ensuring they formed stable solitons and didn't spread across the grid.

This required a delicate balance of forces. If the magnetic attraction was too weak, the solitons would dissolve. If it was too strong, the entire cluster would collapse.

Accordion lattice testing

To see if they had successfully created the solitons, the team used an accordion lattice. This laser grid with adjustable spacing lets researchers stretch the distance between atoms. Once the atoms were far enough apart, the researchers were able to check whether they were trapped in their positions. Although they couldn't see the atoms directly, they shined a resonance laser through the grid. By measuring how the atoms blocked the light, they could see that solitons had formed.

The atoms had formed two distinct stable structures. Some atoms were concentrated into a single point on the grid, while others were distributed across several sites while still acting as a single unit. The clusters remained stable for nearly half a second.

Possibilities for more stability in quantum sensing and transport

According to the team, their work opens up new possibilities for controlling quantum matter, as they note in their paper: "Our results pave the way for exploring a multitude of nonlinear matter-wave excitations in optical lattices, such as lattice breathers and discrete solitons in deep lattice potentials."

The level of control achieved here could eventually allow scientists to design more stable quantum sensors or transport delicate quantum information without it leaking away and losing its quantum properties.