Ultrafast Processing of Hyper-Entangled Bell States at the Optical Bandwidth Limit
The research demonstrates how to generate and detect a high flux of polarization Bell states using broadband hyper-entangled bi-photons correlated in both polarization and time-energy. They use SU(1,1) interferometry for ultra-fast detection, overcoming previous limits of $10^6$-$7$ photons/s. This enables the complete measurement of all triplet Bell states, paving the way for quantum metrology and high-speed quantum communication.