BENGALURU – Indian researchers have demonstrated for the first time how atoms, when pushed to extremely high-energy states, stop behaving independently and begin interacting collectively, a finding that could inform the development of future quantum computers, sensors, and communication devices.
At the 100th energy level and beyond, Rydberg atoms—atoms with outer electrons excited to very high energy states—showed distorted and broadened responses to light, according to scientists from the Raman Research Institute (RRI), an autonomous institute under the Department of Science and Technology (DST). The interactions, previously unobserved at such high levels, indicate that the atoms respond as a collective rather than as individual particles.
“By installing a highly sensitive detection system capable of picking up even a few photons emitted by the atoms, we were able to study Rydberg states with n greater than 100 and measure their signals with a good signal-to-noise ratio,” said Prof. Sanjukta Roy of RRI, who led the experiment with PhD students Silpa B S and Shovan K Barik.
The experiment combined laser and magnetic trapping of rubidium atoms cooled to near absolute zero with light excitation to produce Rydberg states. At lower energy levels, the atoms displayed the expected Autler–Townes splitting pattern, but at higher energies the pattern broke down, revealing inter-atomic interactions.
Theoretical modelling by Prof. Rejish Nath’s team at IISER Pune helped interpret the collective behaviour of the atoms. Researchers said understanding the threshold where atoms begin interacting will be critical for precision in quantum simulations and the design of next-generation quantum devices.
Rydberg atoms, which are significantly larger and more sensitive than ordinary atoms, are central to quantum research because their high sensitivity allows precise measurement but also increases unpredictability. The study shows that by controlling these atoms at near-absolute zero and energising them to extreme states, scientists can observe the transition from isolated to collective behaviour.
The discovery positions India at the forefront of global quantum research and provides a roadmap for designing future quantum technologies, researchers said.
