Photonic quantum computers harness unique quantum features and promise a dramatic increase in speed over classical computers in a variety of computational tasks; they are designed to complete tasks that even a supercomputer would not be able to handle. A challenging aspect in the current research is the required miniaturization of the quantum circuits onto a single chip. Using femtosecond laser inscription of waveguides [J. Phys. B 43, 163001 (2010)], we devise novel schemes for integrated quantum-optical devices that range from lattices for the manipulation of quantum random walks of indistinguishable and entangled photons in one-dimensional [Phys. Rev. Lett. 110, 150503 (2013)] and two-dimensional setting [Phys. Rev. Lett. 112(14), 143604 (2014)] over the implementation of various quantum gates [Sci. Rep. 4, 4118 (2014)] to the implementation of complete quantum computation networks [Nature Photonics 7, 540-544 (2013)]. Only recently, we were able to generate so-called W-states on a chip [Nature Photon 8, 791 (2014)], peculiar quantum states that are particularly useful for secure quantum communication protocols and quantum random number generation.

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Left: Fluorescence image of the possible paths of three entangled photons in a bosonic sampling quantum computation network on a chip [Nature Photon. 7, 540-544 (2013)]. Right: the actual chip.

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