An important motivation for deep learning was the Universal Approximation Theorem which shows, that neural networks can theoretically approximate any function. When it comes to quantum machine learning, a similar statement can be made. Surprisingly a single qubit is sufficient, to perform the classification of arbitrary data distributions.
Universal Approximation Theorem The Universal Approximation Theorem (there are many versions with different constraints) states that the functions which can be expressed by a neural network with a single hidden layer and arbitrarily many units are dense in the space of continuous functions....