South Korean Researchers Use Crystal Trick to Control Quantum Light

Insider Brief

• South Korean researchers have demonstrated a method to control polaritons using ferroelectricity in a perovskite crystal, offering a new approach to scalable quantum devices.
• The team modulated the Rabi oscillation frequency of polaritons by up to 20% and increased oscillator strength by 44% through phase-induced changes in the crystal structure.
• The study, published in Advanced Science and supported by the Samsung Science and Technology Foundation, shows potential for room-temperature quantum technologies without complex external equipment.

A research team from South Korea have demonstrated a method to control polaritons — quantum particles formed from light and matter –by altering the internal structure of a semiconductor crystal, opening the door to more practical and scalable quantum technologies, reports Asia Research News.

The study, published in Advanced Science recently, was conducted by Professor Chang-Hee Cho’s team at Daegu Gyeongbuk Institute of Science and Technology (DGIST), with Ph.D. candidate Hyeon-Seo Choi listed as first author. According to the researchers, the findings offer a new pathway for designing quantum light sources and devices that don’t rely on bulky external components.

“This study goes beyond simply generating polaritons; it demonstrates that their intensity and properties can be controlled through ferroelectricity, a practical approach,” said Chang-Hee Cho. “As control technologies for quantum devices continue to advance, the practical implementation of various quantum-based technologies, such as quantum computers and communication systems, could be accelerated.”

Rabi Oscillation

Polaritons are composite quasiparticles formed when photons couple with excitons — temporary bound states created when an electron is knocked loose, leaving behind a positively charged hole. These hybrid particles behave both like light and matter, moving rapidly while retaining the ability to interact with their environment. Their ability to undergo “Rabi oscillation,” a cyclical transition between light and matter states, makes them attractive candidates for quantum computing, communication systems, and next-generation optical sensors.

The challenge has been that Rabi oscillations are difficult to control without external fields or equipment, limiting their usefulness in compact devices. Cho’s team addressed this by turning to a material called methylammonium lead bromide (MAPbBr₃), a member of the perovskite family of semiconductors known for their phase-transition properties. Like water freezing or boiling, the crystal structure of this material changes depending on temperature or other conditions.

In one of its phases, the material exhibits ferroelectricity, which is the spontaneous electric polarization that arises without the need for an external electric field. The researchers found that this property influences the behavior of excitons, which in turn changes the properties of polaritons, Asia Research News Reports.

Using a specially designed microcavity structure, the DGIST team demonstrated that the phase-induced ferroelectric properties of the perovskite crystal could modulate the Rabi oscillations of polaritons. The oscillation frequency was tunable by up to 20%, while the oscillator strength — the degree of coupling between light and matter — increased by as much as 44%.

Controlling Quantum Behavior

According to the study, these changes were directly tied to the asymmetric crystal structure observed during the ferroelectric phase, confirming that internal material properties could be harnessed to control quantum behavior without the need for additional equipment.

This method, the team reports, could significantly reduce the complexity and cost of quantum devices, particularly those that use light to encode and process information. Because the control mechanism relies on structural changes within the material itself, it is well suited to room-temperature operation—a key factor in scaling quantum technologies beyond the laboratory.

The study was supported by the Samsung Science and Technology Foundation and reflects ongoing efforts across the quantum research community to find simpler, more stable methods for manipulating quantum systems. While many quantum platforms rely on cryogenic environments or precision hardware, the DGIST study points to the possibility of integrated, material-based solutions.

The findings also carry potential implications for photonic AI chips, ultrafast quantum sensors, and compact quantum communication modules, all of which depend on reliable quantum light sources that can operate in everyday environments.