This e-book gathers the lecture notes of classes given on the 2011 summer season institution in theoretical physics in Les Houches, France, consultation XCVI.

What is a quantum laptop? will we say that lasers and transistors are quantum machines? in spite of everything, physicists promote it those units because the major spin-offs of the certainty of quantum mechanical phenomena. although, whereas quantum mechanics needs to be used to foretell the wavelength of a laser and the operation voltage of a transistor, it doesn't intrude on the point of the signs processed by means of those structures. signs contain macroscopic collective variables like voltages and currents in a
circuit or the amplitude of the oscillating electrical box in an electromagnetic hollow space resonator. In a real quantum laptop, the sign collective variables, which either tell the skin at the kingdom of the computer and obtain controlling directions, needs to themselves be taken care of as quantum
operators, simply because the place of the electron in a hydrogen atom. Quantum superconducting circuits, quantum dots, and quantum nanomechanical resonators fulfill the definition of quantum machines. those mesoscopic platforms show a number of collective dynamical variables, whose fluctuations are good within the quantum regime and whose dimension is largely restricted in precision through the Heisenberg uncertainty precept. different engineered quantum platforms according to usual, instead of man made degrees
of freedom may also qualify as quantum machines: trapped ions, unmarried Rydberg atoms in superconducting cavities, and lattices of ultracold atoms. This ebook offers the fundamental wisdom had to comprehend and examine the physics of those novel systems.