I was researching how optical quantum computers work and discovered a KLM protocol that allows for building quantum gates using linear optics elements like mirrors, beam splitters, and phase shifters. However, I was wondering how would we get the same functionality as with superconducting QCs. With superconducting QCs, we have Josephson Junctions - JJs. Those JJs are being interacted with differently so they form a specific gate when that gate operation is needed.
Besides optical JJ, what would be the optical equivalent to Josephson Junction that we could apply quantum gates to? What are the QCs like the ones from Xanadu running on when it comes to physical qubit implementation?