In a major leap for quantum physics, a team of researchers in Italy has succeeded in transforming light into a supersolid — a state of matter that holds both the ordered structure of a solid and the frictionless flow of a liquid. This development represents the first time light has been made to behave in a way that resembles a solid, opening up exciting possibilities for computing, communications, and our understanding of light and matter.
—
What is a Supersolid?
A supersolid is a rare quantum state that combines two seemingly contradictory traits:
Solid-like behavior: particles form a rigid, repeating structure (like in a crystal).
Fluid-like behavior: the material can flow without resistance (no viscosity).
Until now, supersolids have mainly been achieved with ultracold atoms or special atomic condensates in lab settings. What’s new here is accomplishing a supersolid state using light (photons interacting with matter).
—
How Did They Do It?
Here are the key ideas and setup:
1. Coupling light to matter — The researchers used a semiconductor material (gallium arsenide) structured at the nanoscale. Photons from a laser are made to interact with excitations in the material (“excitons”) to create hybrid particles called polaritons. These are part-light, part-matter, which allows some of the unusual quantum behaviors.
2. Photonic crystal structure & energy states — The semiconductor was designed to support several quantum states for the polaritons. At first, most photons occupy the lowest energy state, but as that fills up, others occupy adjacent states of the same energy. This causes the system to break spatial symmetry, producing periodic arrangements in photon density — i.e. a crystal-like pattern.
3. Maintaining coherence and flow — Even with the structure, the light maintains coherence (quantum phase relationships) and shows properties of superfluidity (it flows without viscosity). Those are essential for calling this a supersolid rather than just a patterned light field.
4. Near-absolute zero / driven-dissipative system — The experiments require extremely low temperatures and careful control of dissipation (loss) and driving (supplying energy), because quantum phases are fragile.
—
Why It Matters
This is more than a curiosity. The implications are significant:
Quantum computing & information storage: Structures like this might allow new ways to store light and information, perhaps improving speeds or reducing energy losses.
Optical communication: If light can be controlled more precisely, systems might push past current limits of fiber optics or photonic circuits.
Fundamental physics: The experiment deepens our understanding of how light and matter can combine to produce new phases of matter. Supersolids challenge classical categories like “liquid” or “solid.”
—
What It Isn’t
It’s not “freezing light” in the sense of stopping it outright, or making light into a static, ice-like substance. The experiment does not trap photons permanently like frozen blocks; the photons are part of a system where they interact, flow, and lose energy over time. What is “solid-like” is the organized spatial pattern plus the quantum coherence.
It’s on a very small scale, under very controlled lab conditions, and currently far from everyday use.
—
The Road Ahead
Researchers are keen to explore:
How to maintain and scale up such supersolid light states.
Whether they can be stabilized at higher temperatures or with more robust materials.
Practical devices: maybe new kinds of lasers, switches, or quantum chips that exploit this phenomenon.
The creation of a light–made supersolid is a striking example of how quantum physics continues to reveal surprising behaviors even for something as familiar as light. While the notion of “turning light solid” may sound like science fiction, the actual achievement lies in demonstrating a light-matter state that combines order and motion in new ways. As scientists build on this, we may see advances in quantum technology, optics, and computing that we can barely imagine now.
Source: Trypogeorgos, D., Gianfrate, A., Landini, M., et al. “Emerging supersolidity in photonic-crystal polariton condensates.” Nature, 2025. (Published ~5 March 2025)