One of the challenges to creating and maintaining quantum states is their extreme sensitivity to disorder. Even the smallest imperfections and errors in nanofabrication can hinder the scalability of quantum systems.

To make quantum states more robust to unavoidable imperfections, researchers at CREOL, the College of Optics and Photonics at the University of Central Florida, explored loss engineering as a means to generate and control topological properties of electromagnetic modes. The team, led by professor Andrea Blanco-Redondo, demonstrated a photonic platform that can be used to precisely control optical loss, leading to robust topological properties. “What we have realized is that you can use it to control the loss very precisely, which has allowed us to demonstrate the appearance of topology solely from loss modulation,” Blanco-Redondo said.

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UCF CREOL doctoral student Amin Hashemi Shahraki (left) in the lab with professor Andrea Blanco-Redondo. Courtesy of the University of Central Florida, College of Optics and Photonics.

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The researchers demonstrated that, by modulating loss, non-Hermitian topology could emerge in a photonic system that was topologically trivial in the absence of loss. “What we have done is to observe that topology can appear just because of the presence of loss,” Blanco-Redondo said.

The lossy platform could be a significant step toward understanding and controlling quantum states of light, leading to advancements in sensing, lasing, and other applications.

To introduce controllable loss into the platform, the researchers implemented a non-Hermitian generalization of a model in a programmable integrated photonics platform, using a photonic version of a field-programmable gate array (FPGA). They investigated different periodic and quasiperiodic configurations of the model and observed the emergence of topological edge modes. They explored the resilience of these modes to different kinds of disorder.

When the team modulated the loss in specific ways, it observed the appearance of localized modes of light, which were robust to certain types of disorder. This finding could be an important step toward managing the fragility of quantum states. In the application of quantum computing, for example, reducing the effects of imperfections could move the error rate toward a level necessary to achieve useful computations. “If you can build electromagnetic modes or ways to guide light in a way that is robust to these kinds of imperfections, that could have a tremendous impact,” Blanco-Redondo said.

The team’s findings could be especially impactful for the development of integrated photonic circuits, topological sensors and lasers, and quantum computing applications. Integrated photonic circuits confine light at the nanoscale, where light behaves differently than it does while traveling through free space or inside fiber optics. The confinement of light at such a small scale enables nonlinear light-matter interactions, which can occur when light interacts strongly with matter.

For example, when two photons that come from one laser interact with matter strongly, they essentially disappear and produce two other photons that are quantum-correlated. Through this nonlinear optical process, a state of quantum entanglement is generated.

The ability to realize more robust quantum states could also enable advancements in the field of sensing.

“With classical sensors, there’s basically a noise level that you can never surpass,” Blanco-Redondo said. “When you start using certain quantum properties of light, like superposition, entanglement, or squeezing, there are ways to surpass that classical limit and make sensors that are better than anything classical out there.”

Non-Hermitian topology from optical loss modulation also could be used to advance topological lasers, which have the potential to provide superior performance, efficiency, and stability compared to traditional lasers.

A greater understanding of how light behaves at the quantum level is key to future technological advancements. One example is the ability of quantum computing to leverage principles in which photons can be in multiple places and states simultaneously to achieve vastly enhanced processing power.

“Understanding these things better is going to lead to real advances in quantum computing, quantum sensing, and quantum information science in general,” Blanco-Redondo said.

The research was published in Nature Materials (www.doi.org/10.1038/s41563-025-02278-8).

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