Hadiseh Alaeian

Hadiseh Alaeian, assistant professor in the Elmore Family School of Electrical and Computer Engineering and the Department of Physics and Astronomy at Purdue University, is part of a research team whose work was recently published in PRX Quantum, a journal of the American Physical Society.

The paper, “Collective Enhancement of Photon Blockade via Two-Photon Interactions,” explores a new theoretical path toward creating nonclassical light, a key resource for future quantum technologies such as quantum data transmission, sensing and computing.

At the center of the work is a quantum effect known as photon blockade, a phenomenon in which light is controlled so that photons, the smallest particles of light, pass through a system one at a time or in carefully controlled groups. This degree of control is important because many quantum technologies rely on the ability to generate and control light with extreme precision.

Traditionally, achieving photon blockade has required very strong interactions between light and a single atom or atom-like system. That is difficult to achieve in many practical platforms. Simply adding more atoms does not usually solve the problem, because the effect can become weaker as the system grows.

The research team showed that this limitation can be overcome using a different kind of interaction, known as two-photon light-matter coupling. In their theoretical model, many identical quantum emitters interact collectively with a single optical cavity. Instead of weakening the photon blockade effect, the larger ensemble strengthens it.

The study found that this collective approach can suppress unwanted multiphoton transmission while preserving high light transmission. In other words, the system could produce cleaner quantum light without sacrificing brightness, a common trade-off in other approaches.

“This work shows that collective behavior can be used as an advantage rather than a limitation,” Alaeian said. “By engineering how photons interact with many quantum emitters, we can open new possibilities for generating the kinds of specialized light needed for quantum technologies. The exciting part is that this points toward scalable approaches in systems where strong coupling to a single emitter is difficult.”

The findings are especially relevant to quantum cavity electrodynamics systems, in which light is confined in a small space and interacts with matter. The paper points to potential applications in quantum detection, quantum communication, and quantum computing, where reliable sources of nonclassical light are essential.

The work also identifies decoherence, the loss of delicate quantum behavior due to a system’s interaction with the surrounding environment, as a key factor that will ultimately limit performance. Among those effects, emitter dephasing, which is the loss of synchronization among quantum emitters, was found to be the dominant constraint.

In addition to Alaeian, the paper’s authors are Lijuan Dong of Sapienza University; Aanal Jayesh Shah of Purdue University; Peter Kirton of the University of Strathclyde; and Simone Felicetti of Sapienza University and the Institute for Complex Systems, National Research Council.