  Quantum computer has an amazing potential of fast information processing.
However, realisation of a digital quantum computer is still a challenging
problem requiring highly accurate controls and key application strategies. Here
we propose a novel platform, quantum reservoir computing, to solve these issues
successfully by exploiting natural quantum dynamics, which is ubiquitous in
laboratories nowadays, for machine learning. In this framework, nonlinear
dynamics including classical chaos can be universally emulated in quantum
systems. A number of numerical experiments show that quantum systems consisting
of at most seven qubits possess computational capabilities comparable to
conventional recurrent neural networks of 500 nodes. This discovery opens up a
new paradigm for information processing with artificial intelligence powered by
quantum physics.
