Circuit designs for superconducting optoelectronic loop neurons

TL;DR

This paper proposes superconducting optoelectronic neurons that use single-photon detection and light communication for highly energy-efficient, scalable neural networks capable of brain-like connectivity and high-speed operation.

Contribution

It introduces integrated circuit designs combining superconducting detectors, Josephson junctions, and semiconductor light sources for neural computation and plasticity, demonstrating all components experimentally.

Findings

Achieved complex synaptic and neuronal functions with high energy efficiency.

Enabled connectivity from a neuron to thousands of synapses using microscale light sources.

Projected a scalable neural platform with brain-like connectivity and 30,000 times higher speed.

Abstract

Optical communication achieves high fanout and short delay advantageous for information integration in neural systems. Superconducting detectors enable signaling with single photons for maximal energy efficiency. We present designs of superconducting optoelectronic neurons based on superconducting single-photon detectors, Josephson junctions, semiconductor light sources, and multi-planar dielectric waveguides. These circuits achieve complex synaptic and neuronal functions with high energy efficiency, leveraging the strengths of light for communication and superconducting electronics for computation. The neurons send few-photon signals to synaptic connections. These signals communicate neuronal firing events as well as update synaptic weights. Spike-timing-dependent plasticity is implemented with a single photon triggering each step of the process. Microscale light-emitting diodes and waveguide networks enable connectivity from a neuron to thousands of synaptic connections, and the use of light for communication enables synchronization of neurons across an area limited only by the distance light can travel within the period of a network oscillation. Experimentally, each of the requisite circuit elements has been demonstrated, yet a hardware platform combining them all has not been attempted. Compared to digital logic or quantum computing, device tolerances are relaxed. For this neural application, optical sources providing incoherent pulses with 10,000 photons produced with efficiency of 10$^{-3}$ operating at 20\,MHz at 4.2\,K are sufficient to enable a massively scalable neural computing platform with connectivity comparable to the brain and thirty thousand times higher speed.