Fig. 3: Using the spin-wave scatterer for vowel recognition.

a, b Wave intensity patterns, formed in response to the time-domain excitations (vowels). The scatterer was trained to focus waves to the corresponding outputs. The bar charts show the intensity at the output locations (normalized). The linear regime a (1 mT excitation field) and the nonlinear regime b (50 mT excitation field) performs comparably well on the training data (slight improvement in case of nonlinear waves). c Cross-entropy loss decreases during the training, indicating learning. After 30 epochs (training steps), the nonlinear cases achieve better performance compared to the linear case. Note that a nonzero loss value corresponds to the perfect response, indicated by a dotted line. d Accuracy of vowel recognition on the training and testing data sets. e, f Confusion matrices over the testing data set (123 vowel samples). g Accuracy of vowel recognition (test set) as a function of excitation amplitude.