Supersolid Light: Scientists Transform Light into Quantum Matter | March 2025

A supersolid is one of the most enigmatic phases of matter ever theorized. It possesses a rare duality that blends characteristics typically found in mutually exclusive states:

1. Solid Structure: Atoms or particles are arranged in a consistent, rigid crystalline lattice — they maintain a fixed, ordered pattern like any solid material.

2. Superfluid Behavior: The material flows with zero viscosity, allowing completely frictionless movement — like a liquid with no resistance whatsoever.

The Paradox:

This combination seems impossible — how can something have a rigid structure yet flow without friction? In a supersolid, some particles form the rigid lattice while others move freely through it, creating a material that retains shape like a solid while flowing like a superfluid.

Historical Context:

Originally theorized decades ago, supersolids were mostly associated with ultra-cold atomic systems like Bose-Einstein condensates (achieved near absolute zero temperature). What makes this discovery revolutionary is that scientists have now created a supersolid from light — an entity long thought to lack mass, structure, or the ability to behave like matter.

Researchers at CNR-INO, CNR-Nanotec, and the University of Pavia achieved this feat by engineering a system that manipulates photons into behaving like quantum particles of matter.

Step-by-Step Process:

Step 1 — Microcavity Confinement:

Scientists used semiconductor nanostructures called microcavities to confine and control light. These are tiny chambers made of mirrors that trap photons, bouncing them back and forth.

Step 2 — Exciton Interaction:

Inside the microcavities, photons interacted with excitons — these are bound pairs of electrons and “holes” (missing electrons) in the semiconductor. Think of excitons as matter-side partners for the photons.

Step 3 — Polariton Formation:

The photon-exciton interaction created polaritons — hybrid light-matter quasiparticles that have properties of both light and matter. Polaritons have effective mass (unlike pure photons) and can interact with each other.

Step 4 — Quantum Condensation:

These polaritons then condensed into quantum droplets that exhibited both ordered structure (like a solid) and frictionless flow (like a superfluid) — creating the world’s first supersolid made of light!

The Result:

A lattice of supersolid light droplets — coherent, stable, and mobile, behaving with properties never seen before in optical systems.

Key Components Used:

1. Semiconductor Microcavities:

Tiny mirror-based structures that trap photons. Made from semiconductor materials (like gallium arsenide). Allow precise control over light-matter interactions at quantum level.

2. Excitons (Electron-Hole Pairs):

When light hits a semiconductor, it can excite an electron, leaving behind a “hole.” The electron and hole are bound together by electromagnetic attraction — this pair is called an exciton. Excitons provide the “matter” component that photons need to behave like particles with mass.

3. Polaritons (Hybrid Quasiparticles):

When photons strongly couple with excitons, they form polaritons — particles that are part light, part matter. Polaritons have some properties of photons (speed, coherence) and some properties of matter (mass, interaction ability). They can undergo Bose-Einstein condensation — forming a collective quantum state.

What’s Different from Previous Supersolids:

Previous supersolid experiments required ultra-cold atoms near absolute zero (-273°C), high vacuum environments, magneto-optical traps, and Bose-Einstein condensates of heavy atoms. This light-based approach works at relatively higher temperatures and uses solid-state semiconductor technology — making it potentially more practical for real-world applications.

The creation of light-based supersolid offers promising real-world applications across several advanced domains:

1. Quantum Computing:

Supersolid light droplets exhibit quantum coherence and structural stability, making them potential candidates for robust qubit systems. These light-based qubits could resist environmental decoherence (a major problem in current quantum computers), maintain consistent states over longer periods, and support scalable, fault-tolerant quantum architectures.

2. Photonic Circuits:

Integration of supersolid polariton condensates could lead to zero-energy-loss circuits. Since supersolids flow without friction, light signals could travel through circuits with virtually no loss — enabling ultra-efficient computing and communication systems.

3. Photonic Energy Storage:

Because these systems involve light locked in matter-like behavior, they might enable ultrafast photonic circuits, improve on-chip energy storage for microdevices, and support light-based logic systems in optoelectronics.

4. Quantum Internet:

Supersolid light could become the foundation for quantum internet systems, enhancing the reliability of photon-based encryption and quantum key distribution.

5. Next-Gen Materials Science:

Understanding structured quantum light could inspire self-assembling nanomaterials, adaptive materials that change properties under different conditions, and quantum-responsive surfaces for smart technology applications.

Why This Discovery Is Revolutionary:

1. Redefines Light Itself:

For centuries, light was understood as massless energy — either waves or particles (photons) that travel through space without structure. This discovery shows light can behave like structured matter with crystalline organization.

2. First Light-Based Supersolid:

Previous supersolids required ultra-cold atoms near absolute zero. This is the first time a supersolid has been created from light, opening entirely new research directions.

3. Bridges Theory and Application:

As Prof. Dario Gerace (University of Pavia) noted: “This bridges the gap between abstract quantum theories and practical photonic technologies.”

4. Room for Practical Implementation:

Unlike ultra-cold atomic systems, semiconductor-based polariton systems can potentially work at higher temperatures and be integrated into existing chip technology.

Lead Researchers:

Dr. Iacopo Carusotto (CNR-INO), Dr. Dimitrios Trypogeorgos (CNR-Nanotec), Dr. Daniele Sanvitto (CNR-Nanotec), and Prof. Dario Gerace (University of Pavia) led this groundbreaking research.