Spintronics for image recognition : performance benchmarking via ultrafast data-driven simulations

We present a demonstration of image classification using a hardware-based echo-state network (ESN) that relies on spintronic nanostructures known as vortex-based spin-torque oscillators (STVOs). Our network is realized using a single STVO multiplexed in time. To circumvent the challenges associated with repeated experimental manipulation of such a nanostructured system, we employ an ultrafast data-driven simulation framework called the data-driven Thiele equation approach (DD-TEA) to simulate the STVO dynamics. We use this approach to efficiently develop, optimize and test an STVO-based ESN for image classification using the MNIST dataset. We showcase the versatility of our solution by successfully applying it to solve classification challenges with the EMNIST-letters and Fashion MNIST datasets. Through our simulations, we determine that within a large ESN the results obtained using the STVO dynamics as an activation function are comparable to the ones obtained with other conventional nonlinear activation functions like the reLU and the sigmoid. While achieving state-of-the-art accuracy levels on the MNIST dataset, our model's performance on EMNIST-letters and Fashion MNIST is lower due to the relative simplicity of the system architecture and the increased complexity of the tasks. We expect that the DD-TEA framework will enable the exploration of more specialized neural architectures, ultimately leading to improved classification accuracy. This approach also holds promise for investigating and developing dedicated learning rules to further enhance classification performance.