  In this article, we proposed a programmable 16-channel photonic solver for
quadratic unconstrained binary optimization (QUBO) problems. The solver is
based on a hybrid optoelectronic scheme including a photonic chip and the
corresponding electronic driving circuit. The photonic chip is fabricated on
silicon on insulator (SOI) substrate and integrates high-speed electro-optic
modulators, thermo-optic phase shifters and photodetectors to conduct the
16-dimensional optical vector-matrix multiplication (OVMM). Due to the parallel
and low latency propagation of lightwave, the calculation of the QUBO cost
function can be accelerated. Besides, the electronic processor is employed to
run the heuristic algorithm to search the optimal solution. In the experiment,
two 16-dimensional randomly generated QUBO problems are solved with high
successful probabilities. To our knowledge, it is the largest scale of
programmable and on-chip photonic solver ever reported. Moreover, the computing
speed of the OVMM on photonic chip is ~2 TFLOP/s. It shows the potential of
fast solving such optimization problems with integrated photonic systems.
