Supersolids, a bizarre and fascinating quantum state of matter, have now taken a new, mind-bending form: light itself. In a groundbreaking experiment, scientists have successfully transformed light into a supersolid, a development that could pave the way for advancements in quantum and photonic technologies.

Supersolids, a state previously only observed in atoms, combine the ordered structure of solids with the free-flowing properties of liquids. These extraordinary materials defy traditional classifications of matter, offering a crystalline arrangement like a solid while also exhibiting the fluid-like ability to flow without losing their shape—something that seems counterintuitive at first glance.

“We can imagine the supersolid as a fluid composed of coherent quantum droplets periodically arranged in space,” explains Iacopo Carusotto, an atomic and optical physicist at the University of Trento in Italy. These droplets, he adds, “are able to flow through an obstacle without undergoing perturbations, maintaining their spatial arrangement and mutual distance unchanged, much like in a crystalline solid.”

Until now, supersolids had only been created using atoms. However, a team of scientists at the National Research Council (CNR) in Italy has taken this one step further by creating the first-ever supersolid made of photons, the particles of light.

This achievement requires a bit of quantum wizardry to fully understand. After all, light is not matter but energy, which makes the process of transforming it into a supersolid far from straightforward. Instead of simply manipulating free photons in the air, the researchers had to “couple” the photons with matter. They used a laser to generate photons, which were directed at a semiconductor material—gallium arsenide. This material provided the necessary conditions for photons to interact with excitations in the material, forming quasiparticles called polaritons.

Previously, similar setups have been used to turn light into a superfluid, a state in which light flows without resistance. However, turning it into a supersolid is a much more complex feat that requires a few additional steps.

The gallium arsenide used in the experiment was specially designed to manipulate photons into three distinct quantum states. At first, the photons enter a state with zero momentum, but as this state begins to “fill up,” pairs of photons spill into two adjacent quantum states. This interaction leads the polaritons to condense into a unique state referred to as a “bound state in the continuum” (BiC), a key step in the formation of the supersolid.

This development not only demonstrates the potential of creating supersolids from light but also opens the door to future applications in quantum computing, advanced photonics, and other cutting-edge technologies that rely on the manipulation of light and matter at the quantum level. As scientists continue to explore these exotic states of matter, we may be on the verge of revolutionary breakthroughs that could reshape our understanding of physics and technology.

By Impact Lab