In other words, quantum metamaterials incorporate quantum coherent states in order to control and manipulate electromagnetic radiation. With these materials, quantum information processing is combined with the science of metamaterials (periodic artificial electromagnetic materials). The unit cells can be imagined to function as qubits that maintain quantum coherence "long enough for the electromagnetic pulse to travel across". The quantum state is achieved through the material's individual cells. As each cell interacts with the propagating electromagnetic pulse, the whole system retains quantum coherence.