In the past few years, networks of optical parametric oscillators (OPOs) have been successfully used to simulate the classical Ising Hamiltonian leading to a platform that may be used as a special-purpose computer. In this talk, we will overview the fundamental properties of OPOs at degeneracy that enable simulation of the Ising Hamiltonian [1-3]. We will discuss the concept of time-multiplexed OPO networks , which in combination with the measurement-feedback architecture, has led to a special implementation of large-scale Ising machines  that are being studied extensively . We will also overview the potentials of OPO networks in realization of a wide range of quantum states, from the well-known squeezed vacuum and multi-mode entangled states to less-explored highly-desired Cat states and present a potential path toward scalable quantum photonic engineering using them. We will discuss recent numerical studies of ultra-short pulse OPOs in the highly-nonlinear quantum regime  and present some of the practical benefits and challenges associated with using them as the building block of a quantum photonic platform.
 A. Marandi et al., “Network of time-multiplexed optical parametric oscillators as a coherent Ising machine,” Nature Photonics 8.12 (2014): 937-942.
 P. McMahon, A. Marandi* et al., “A fully programmable 100-spin coherent Ising machine with all-to-all connections,” Science 354.6312 (2016): 614-617.
 R. Hamerly, T. Inagaki, P.L. McMahon*, et al., “Experimental investigation of performance differences between Coherent Ising Machines and a quantum annealer,” arXiv:1805.05217 (2018).
 T. Onodera*, E. Ng*, et al., “Nonlinear quantum behavior of ultrashort-pulse optical parametric oscillators,” arXiv:1811.10583 (2018).