“Solid light” refers to light behaving as if it were a solid material. In practice, this means photons (light particles) are made to interact or arrange in an ordered state, exhibiting properties like rigidity or crystallinity that we normally associate with solids . This counter-intuitive idea has been explored theoretically for over a decade – for instance, researchers in 2007 predicted that under the right conditions photons could “repel each other…and form a crystal,” drawing an analogy to a phase transition like water freezing into ice . Only in the last few years, however, have experiments succeeded in solidifying light into tangible quantum states of matter. These achievements are enabling new ways to study quantum physics and potentially develop advanced technologies.
Recent Scientific Research (2022–2025) on Solid Light
Photonic Supersolid (2025 – Nature):
In a breakthrough reported in Nature (March 2025), an international team turned laser light into a supersolid, a quantum phase that is both solid and superfluid . Supersolids have a crystal-like structure yet can flow without friction, and until now they had only been created with ultracold atoms. The new experiment instead used photons coupled to a semiconductor chip. When researchers fired a laser into an etched gallium arsenide waveguide, the light interacted with the material to form polaritons (hybrid light-matter quasiparticles) that spontaneously organized into a lattice . The resulting “solid light” exhibited a spatially periodic density (like a crystal) and maintained a single coherent quantum phase (like a superfluid), satisfying the two key hallmarks of a supersolid. “We actually made light into a solid. That’s pretty awesome,” said Dimitrios Trypogeorgos, a physicist on the team. This photonic supersolid is the first ever observed, providing a novel platform to explore exotic quantum matter in a driven, room-temperature system. The research, led by Italy’s CNR Nanotec institute with collaborators from universities in Europe and Princeton in the U.S., was published in Nature.
Photon-Photon Interactions and “Light Matter” (2022–2023):
A key requirement for solidifying light is to induce strong interactions between photons, which normally do not interact. Recent studies have achieved this using specialized media that mediate photon-photon forces. For example, a 2023 paper in Science demonstrated that when photons are sent through an ultracold, dense cloud of rubidium atoms, they can interact strongly enough to create quantum vortices – essentially causing two light pulses to swirl around each other as if they were fluid particles with mass. Researchers at Israel’s Weizmann Institute found that pairs of photons propagating through the atomic gas imprinted phase twists on one another, producing vortex-like phase patterns indicative of inter-photon forces. This experiment, published in Science (July 2023), was hailed as evidence of a “quantum fluid of light” where photons behave collectively much like a superfluid liquid. Such strongly interacting photonic fluids are a step toward forming solid-light states and could be harnessed for optical quantum computing – indeed, the team noted that a full $180^\circ$ phase shift between two photons (achieved in optimal conditions) is a desirable effect for photon-based logic gates.
Another advance came in late 2022, when a group led by Google/Caltech researchers reported in Nature the formation of bound states of microwave photons – essentially “photonic molecules.” By using superconducting qubits as an intermediary, they induced two and even three microwave photons to bind together into stable composites. This “robust bound state of interacting photons” is a form of solid light because the photons become highly correlated, sharing a joint quantum state as if they were a single particle. The result, published in Nature (Dec 2022), builds on earlier demonstrations in circuit quantum electrodynamics and shows that even in a chip-based system, light can exhibit the kind of phase transitions (in this case, a dissipation-induced crystallization of photons) that we normally see in solid matter. These peer-reviewed studies underscore a growing trend: photons in carefully engineered setups can mimic the behaviors of electrons in solids, from forming crystal-like band structures to entering new phases of matter.
Optical Lattices and Simulated Solids:
A slightly different angle on “solid light” is using light to create solids or simulate solid-state environments. In June 2023, Scientific American featured an article by physicist Charles D. Brown II describing how laser light can form optical lattices – periodic light intensity patterns – that trap atoms and make them behave as if in a crystalline solid. By arranging interfering laser beams, researchers can create a light-made lattice (essentially a crystal of light) for ultracold atoms to hop around. Brown’s team at Berkeley used this approach to construct a “photonic graphene,” an optical lattice with the same honeycomb pattern as carbon atoms in graphene, and loaded ultracold atoms into it. This allowed them to slow down and visualize quantum processes (like electron tunneling and the quantum Hall effect) that would be too fast to see in a real solid. Such experiments don’t solidify light itself, but instead use light as the scaffolding of a synthetic solid. They demonstrate the versatile role of light in quantum simulations: optical lattices of “solid light” have become a vital tool for emulating and studying complex materials in a highly controlled way.
Potential Applications and Implications
The ability to make light behave like a solid could open doors to new technologies and deeper understanding in physics. Because photons do not normally interact, creating solid-light systems offers a unique testbed to study many-body quantum physics in a controlled way. Researchers emphasize that photonic platforms can bridge fundamental science and practical technology. “Realizing this exotic state in a fluid of light…perhaps [we will] be able to exploit its unique characteristics for possible applications in new light-emitting devices,” said Dario Gerace of University of Pavia. One immediate use of “solid” light is as quantum simulators – by mimicking complex solid-state phenomena with light, scientists can probe them more easily and even observe new effects. For instance, simulating graphene with an optical lattice (solid light) allows direct visualization of electron-like behavior at a larger scale. This could aid the design of novel materials or help answer open questions in condensed matter physics.
Looking ahead, photonic supersolids and strongly correlated photon systems might play roles in quantum computing and communications. Light-based supersolids offer the enticing prospect of combining the coherence of light with an ordered structure, potentially useful for robust quantum memory or processing. Some scientists speculate that supersolid light could serve as ultra-stable “coolant” environments for qubits or as elements in neuromorphic computing architectures. The recent Nature study noted that their non-equilibrium photonic crystal platform “paves the way for exploring quantum phases of matter in non-equilibrium systems” and could “bridge the gap between fundamental science and practical applications.” . In interviews, the authors mentioned future work to examine the excitations (phonons) in the photonic supersolid, which could inform the development of advanced photonic devices and sensors.
Solid-light systems might also enable ultra-efficient energy transport and novel optical circuits. Since photons in a superfluid-like state can flow without loss, while arranged in a regular structure, one could envision light-based channels that conduct signals or energy with zero resistance. This could benefit optical computing, where light replaces electrons to eliminate resistive heating. Moreover, because the solid-light phase transition can be controlled (by tuning laser input, cavity parameters, etc.), engineers might use it to switch optical properties on and off – forming the basis of new optical switches or memory elements. As one science writer noted, harnessing the “weirdness of quantum physics” in solid light could lead to “ultra-efficient energy transport and novel computing systems” in the long run.
It’s important to stress that these applications are still speculative. The current solid-light demonstrations occur in specialized lab setups (often at low temperatures or using nanofabricated structures). But the rapid progress in the last few years is encouraging. Achieving a room-temperature photonic supersolid suggests that quantum states of light can be made more accessible outside of extreme conditions . As techniques improve, we may see “hard light” being integrated into optical chips or quantum devices. In short, solid light is both a fundamental scientific breakthrough and a stepping stone toward future photonic technology. Researchers are continuing to refine these systems, investigate their properties (e.g. stability, excitations, interactions with other media), and explore new ways to use light’s solid-like behavior for innovation in science and engineering.
Sources and Further Reading
- Trypogeorgos et al., Nature (2025): “Emerging supersolidity in photonic-crystal polariton condensates.” Nature 639, 337–341 (2025). First experimental demonstration of a photonic supersolid (A supersolid made using photons – Universität Innsbruck) (World First: Physicists Create a Supersolid Out of Light : ScienceAlert).
- Drori et al., Science (2023): “Quantum vortices of strongly interacting photons.” Science 381, 193–198 (2023). Observation of vortex behavior in a photon fluid via strong Rydberg-mediated interactions (Study of photons in quantum computing reveals that when photons collide, they create vortices)
- Morvan et al., Nature (2022): “Formation of robust bound states of interacting microwave photons.” Nature 612, 240–245 (2022). Creation of “photonic molecules” (bound photon states) in a superconducting circuit ((PDF) Formation of robust bound states of interacting microwave …).
- Scientific American (June 1, 2023): “Physicists Make Matter out of Light to Find Quantum Singularities.” Explains how optical lattices (light patterns) can emulate solid-state physics (Physicists Make Matter out of Light to Find Quantum Singularities | Scientific American).
- New Scientist (Mar 2025): Coverage of the photonic supersolid breakthrough (article ID 2470908) (Scientists Just Turned Light Into a ‘Supersolid’: Both Solid and Liquid at The Same Time). Highlights the significance of making light act like a solid for the first time.
- ScienceAlert (Mar 14, 2025): “World First: Physicists Create a Supersolid Out of Light.” News article summarizing the Nature 2025 result (World First: Physicists Create a Supersolid Out of Light : ScienceAlert).
- Phys.org (Mar 6, 2025): “Laser light made into a supersolid for the first time.” by Bob Yirka. Details the experimental setup and includes a Nature briefing link (Laser light made into a supersolid for the first time).
- Live Science (Mar 13, 2025): “Scientists turn light into a ‘supersolid’ for the 1st time ever: What that means, and why it matters.” by Damien Pine (Scientists turn light into a ‘supersolid’ for the 1st time ever: What that means, and why it matters | Live Science) . Accessible overview of the photonic supersolid discovery.
- ZME Science (Mar 6, 2025): “Scientists just turned light into a ‘supersolid’…”. Explains the result and its context in lay terms (Scientists Just Turned Light Into a ‘Supersolid’: Both Solid and Liquid at The Same Time), with quotes from researchers.