US Patent 11501198 Generation of an entangled photonic state from primitive resources

An apparatus includes a plurality of first optical devices and a second optical device. Each first optical device includes a respective first pair of waveguides comprising a respective first waveguide and a respective second waveguide that are coupled together, a respective second pair of waveguides comprising a respective third waveguide and a respective fourth waveguide that are coupled together, and a first fusion gate that includes a detector. Each first fusion gate is configured to perform a fusion on the respective second waveguide and the respective third waveguide of a respective first optical device. The fusion produces a detection pattern for the respective first optical device. The apparatus further includes a multiplexer to select a respective first optical device of the plurality of first optical devices based at least in part on the detection pattern for the respective first optical device and output photons from the respective first optical device.