Abstract: An apparatus for combined digital and optical processing of a cryptocurrency data block includes a digital processor that computes a hash vector from the cryptocurrency data block; a laser and splitter that produces optical input signals; optical modulators that binary phase-shift key modulate the optical input signals based on the hash vector; a photonic matrix multiplier circuit that performs an optically perform a discrete matrix-vector product operation on the modulated optical input signals to produce optical output signals, where the discrete matrix-vector product operation is defined by matrix elements limited to K discrete values, where 2?K?17; and photodetectors and comparators that perform optoelectronic conversions of the optical output signals to produce corresponding digital electronic output signals. The digital processor performs a second hash computation on an XOR result between the digital electronic output signals and the hash vector to produce a proof of work result.

Abstract: Improved training of optical neural networks is provided. In one example: 1) we choose input and target vectors, we program those into an input vector generator and a measurement unit, respectively, we turn on the optical input source power, and we monitor the electrical signal representing the cost function. 2) we can then modulate two or more controllable elements inside the optical network at different frequencies and look for the size and sign of the corresponding distinct AC variations in the measured cost function, simultaneously giving us the gradients with respect to each element.