Flying-qubit gates distributive over photonic waveshapes

Photons, acting as "flying qubits" in propagation geometries such as waveguides, appear unavoidably in the form of wavepackets (pulses). The shape of the photonic wavepacket, as well as possible temporal/spectral correlations between the photons, play a critical role in successful scalable computation. Currently, unentangled indistinguishable photons are considered as a suitable resource for scalable photonic circuits. Here we show that using so called coherent photon conversion, it is possible to construct flying-qubit gates, which are not only insensitive to waveshapes of the photons and temporal/spectral correlations between them, but which also fully preserve these waveshapes and correlations upon the processing. This allows to use photons with correlations and purity in a very broad range for a scalable computation. Moreover, such gates can process entangled photonic wavepackets even more effectively than unentangled ones.