All-optical Ising machine by spatial light modulation

A broad class of computationally intractable problems maps to the search of the ground state of a spin system. Quantum and classical setups that evolve according to an Ising Hamiltonian are thus emerging as novel computing architectures for solving combinatorial optimizations that cannot be tackled on large scales by conventional hardware. Among these, photonic platforms can process data at light speed and in parallel, through multiple spatial or frequency channels. However, the realized photonic Ising machines either involve a limited number of spins or electronic spin couplings or lack of scalability.

Here, we make use of optical spins that are encoded and controlled by spatial light modulation to realize a large-scale all-optical Ising machine [1]. We implement photonic spin configurations with an unprecedented number of interacting nodes that settle in the corresponding Ising ground state. The setup, which is based on the sole spatial coherence of light, suggests a scalable and efficient approach for optical computing. Our results open the route to Ising machines that exploit spatial degrees of freedom of light for parallel spin processing.

[1] D.Pierangeli et al., Large-scale photonic Ising machine by spatial light modulation, Phys. Rev. Lett. 122, 213902 (2019)