  We propose and fully analyze the simplest technique to date to generate
light-based universal quantum computing resources, namely 2D, 3D and, in
general, n-hypercubic cluster states. The technique uses two standard optical
components: first, a single optical parametric oscillator pumped below
threshold by a monochromatic field, which generates Einstein-Podolsky-Rosen
entangled states, a.k.a. two-mode-squeezed states, over the quantum optical
frequency comb; second, phase modulation at frequencies multiple of the comb
spacing (via RF or optical means). The unprecedented compactness of this
technique paves the way to implementing quantum computing on chip using quantum
nanophotonics.
