Programmable non-abelian ‘braiding’ of light demonstrated on photonic integrated circuit
Researchers at Seoul National University have demonstrated programmable non-Abelian braiding of light states on a photonic integrated circuit (PIC), marking a significant advance in topological photonics and defect-resilient optical computing.
The work, published in Physical Review Letters, shows that non-Abelian physics, where the outcome of operations depends on their sequence, can be classically emulated within an integrated photonic platform.
The team, led by Prof. Sunkyu Yu and Prof. Namkyoo Park, in collaboration with researchers from the University of Seoul and the University of Exeter, implemented a programmable spinor lattice that enables matrix-valued control of couplings between optical modes.
By engineering evanescent coupling between pseudo-spin states, the researchers created a photonic building block capable of universal matrix operations incorporating both amplitude and phase. This allowed them to realise optical “braiding” operations, a key computational mechanism in topological quantum computing.
Non-Abelian systems are of particular interest because their operation depends on sequence, providing a route to robust, error-resistant information processing.
In conventional large-scale PICs, fabrication imperfections and device interactions can accumulate errors and degrade reproducibility. By leveraging topological properties, the proposed platform offers enhanced resilience to defects while maintaining programmability.
The team also observed a phenomenon described as a non-Abelian interface at the boundary between distinct topological materials, where protected optical states hybridise and reopen an energy bandgap.
This behaviour introduces a new degree of freedom for controlling light in integrated systems and could support both stable operation and flexible design in future photonic processors.
According to the researchers, the platform establishes a direct connection between topological physics, non-Abelian dynamics and reconfigurable PICs.
The approach may enable experimental verification of complex topological quantum operations and support emerging applications in photonic AI and high-dimensional optical information processing.
