Superconducting Optoelectronic Neurons IV: Transmitter Circuits
This work addresses the need for efficient signal transmission in superconducting neural networks, representing an incremental advancement in circuit design for neuromorphic computing.
The paper tackles the problem of converting small current pulses from superconducting optoelectronic neurons into light signals for neural network communication, achieving neuronal firing speeds of at least 20 MHz with low power density compatible with standard cryogenic cooling at 4.2 K.
A superconducting optoelectronic neuron will produce a small current pulse upon reaching threshold. We present an amplifier chain that converts this small current pulse to a voltage pulse sufficient to produce light from a semiconductor diode. This light is the signal used to communicate between neurons in the network. The amplifier chain comprises a thresholding Josephson junction, a relaxation oscillator Josephson junction, a superconducting thin-film current-gated current amplifier, and a superconducting thin-film current-gated voltage amplifier. We analyze the performance of the elements in the amplifier chain in the time domain to calculate the energy consumption per photon created for several values of light-emitting diode capacitance and efficiency. The speed of the amplification sequence allows neuronal firing up to at least 20\,MHz with power density low enough to be cooled easily with standard $^4$He cryogenic systems operating at 4.2\,K.