  The parameters of a quantum system grow exponentially with the number of
involved quantum particles. Hence, the associated memory requirement goes well
beyond the limit of best classic computers for quantum systems composed of a
few dozen particles leading to huge challenges in their numerical simulation.
This implied that verification, let alone, design of new quantum devices and
experiments, is fundamentally limited to small system size. It is not clear how
the full potential of large quantum systems can be exploited. Here, we present
the concept of quantum computer designed quantum hardware and apply it to the
field of quantum optics. Specifically, we map complex experimental hardware for
high-dimensional, many-body entangled photons into a gate-based quantum
circuit. We show explicitly how digital quantum simulation of Boson Sampling
experiments can be realized. Then we illustrate how to design quantum-optical
setups for complex entangled photon systems, such as high-dimensional
Greenberger-Horne-Zeilinger states and their derivatives. Since photonic
hardware is already on the edge of quantum supremacy (the limit beyond which
systems can no longer be calculated classically) and the development of
gate-based quantum computers is rapidly advancing, our approach promises to be
an useful tool for the future of quantum device design.
