A team of Italian scientists has achieved something never seen before in the world of physics—they have made light behave like a supersolid, a rare state of matter. Their discovery, published in the Nature journal challenges our understanding of light and matter.
A supersolid is a strange state of matter that has the properties of both a solid and a liquid. It flows like a liquid but retains a solid structure. Until now, scientists have only observed this state in extremely cold gases. This new research proves that light, something we usually think of as weightless and intangible, can also behave as a supersolid.
Physicists Antonio Gianfate of CNR Nanotec and Davide Nigro of the University of Pavia, who led the study, explained, “This is only the beginning of understanding supersolidity.” This discovery is expected to open new doors in quantum physics and light-based technologies.
Freezing a liquid typically means lowering its temperature until it becomes solid. However, this experiment required something far more complex. The researchers worked in extreme conditions near absolute zero—the coldest possible temperature, at which atoms almost stop moving.
Absolute zero is measured as 0 Kelvin (K), -273.15°C, or -459.67°F. Scientists cannot reach absolute zero exactly, but they can get very close using advanced laboratory techniques.
Supersolids were first predicted in the 1960s and were first observed in 2017 in special gases. The Italian researchers wanted to see if they could create similar conditions for light using a special material called a semiconductor.
“We decided to investigate whether these conditions can be achieved in a photonic semiconductor platform (in which photons are conducted in a similar way to electrons) to enable photons to behave as a supersolid,” the researchers stated.
By using a carefully designed gallium arsenide structure with tiny engineered ridges, they managed to control how light and matter interact. When they shone a laser beam onto this structure, they created hybrid light-matter particles known as polaritons. These particles started forming patterns, showing supersolid behaviour.
This breakthrough is based on a concept known as the Bose-Einstein condensate (BEC), where particles move together as one unit at extremely low temperatures. The researchers observed that when too many photons (particles of light) were present, they started interacting in an unusual way, forming satellite condensates.
The scientists explained, “These photons form satellite condensates that have opposite nonzero wavenumbers but the same energy (they are isoenergetic).” This means the light particles arranged themselves in a way that is characteristic of a supersolid.
This finding changes the way scientists think about light and opens up exciting new possibilities for quantum technology. Supersolid light could change fields such as quantum computing, optical circuits, and advanced photonic devices.
The ability to manipulate light in this way could have enormous implications for future technology. Scientists believe that supersolid-based photonic systems could provide a more stable platform for qubits, the building blocks of quantum computers. This could lead to major advancements in computing power and speed.
Beyond quantum computing, this discovery could improve optical circuits, making light more controllable and stable for future devices. Researchers are now focusing on refining their techniques to make supersolid light more stable and practical for real-world applications.
The Italian researchers says “The supersolid state emerges, and a spatial modulation in the density of photons in the system occurs that is characteristic of the supersolid state,” they concluded. This means that the properties of supersolid light can be further explored to create new materials and technologies.
