Programming atoms with light: physicists find a way to control quantum states without magnetic fields
A group of researchers from the Faculty of Physics at Vilnius University has presented a theoretical model that fundamentally changes the approach to controlling quantum systems. Instead of the traditional use of external magnetic fields, scientists propose "programming" atoms using light, opening new horizons for quantum communications and computing.
The essence of the method lies in a two-stage process: first, a light beam sets a specific state of the atomic medium, after which this pre-prepared medium alters the shape and polarization of complex laser beams. The key element of the model is optical vortices—laser beams with a spiral wavefront structure, where intensity drops to zero at the center. The size of this dark region is determined by the topological charge, which "can take any positive or negative integer values," providing virtually unlimited possibilities for encoding information.
In practice, this means the ability to obtain up to 10,000 different states, enabling the use of qudits—multi-level units of quantum information that generalize classical qubits. Instead of a binary system with two states, qudits open access to more capacious and robust quantum encoding.
To control vector vortices, the researchers modeled the interaction of a beam with an atomic gas, where atoms have three energy levels. In such a model, the prepared medium inherits the spatial pattern of light: in some areas, atoms intensely absorb radiation, while in others they become almost transparent. A feedback loop emerges—the atomic response restructures the beam itself, transforming a simple ring structure into a complex petal pattern with several bright regions around the center. The polarization structure also changes.
Previously, such control required powerful external magnetic fields and bulky equipment. Now, all control is achieved exclusively with light, significantly simplifying experimental setups and enhancing their compactness.
Analytical conclusion: Theoretically, this development paves the way for creating faster quantum processors, highly secure quantum communication networks, and ultra-precise optical sensors. If the model is successfully implemented in practice, we will witness a paradigm shift in quantum technologies—from cumbersome magnetic systems to compact optical solutions. However, the question of scaling and stability of such systems in real-world conditions remains open. As an expert, I believe this approach could become the key to the practical realization of quantum computing within the next 5–7 years.