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Title of the thesis: Designing quantum sources via integrated photonics with non-Hermitian topological protection

Thesis defender: Elizabeth Pereira 
Opponent: Professor Nuno Miguel Machado Reis Peres, University of Minho, Portugal
Custos: Assistant Professor Jose Lado, Aalto University School of Science

Turning optical loss into a resource for topological photonics 

Energy loss is unavoidable in real physical systems and is normally considered something to be minimized. This thesis explores a different strategy: instead of simply fighting loss, it shows how carefully controlling it can be used to create new states of light. In particular, engineered optical loss can generate topological edge states that are protected against certain types of disorder. 

The concept was demonstrated experimentally on a programmable integrated photonic chip made of coupled optical resonators. By controlling how much light is lost at different locations, topological edge states were created through loss itself. The thesis also develops machine-learning methods that use measured optical spectra to determine the loss and resonant frequencies of individual resonators, helping to characterize complex photonic systems. 

The results offer a new way of thinking about loss: rather than being only a limitation, it can become a tool for designing photonic systems with unusual and robust properties. This could contribute to future programmable photonic technologies and, in the longer term, more robust optical and quantum-information platforms.

Keywords: Non-Hermitian Physics, Integrated Photonics, Topological Insulators, Supervised Machine-Learning

Thesis available for public display 7 days prior to the defence at . 

Contact Information: 
elizabeth.pereira@aalto.fi