Abstract: After a brief introduction to the properties of ultracold atomic systems, in the first part of the talk I discuss how to implement in such systems several types of quantum devices, including Bosonic and Fermionic Josephson junctions, Y-junctions of atomic wires, gyroscopes and atom circuits. In the second part I discuss some applications of quantum gases in the field of quantum simulations, focusing on the implementation of one-dimensional systems and lattice models with tunable parameters.