Since the 80s, progresses in nanofabrication and measurement techniques have reached the point where it is now possible to observe quantum effects in the behavior of electronic devices.

This occurs when the coherence length, which is the length over which an electron retains its quantum behavior, becomes comparable to the size of the system. It is then no longer possible to treat it as a quantum particle like in the old theory of electronic transport developed in the spirit of Boltzmann approach to classical transport.

1. • Electron quantum optics
   

2. • Cavity quantum electrodynamics
   

3. • Decoherence of superconducting circuits

One instead has to develop an approach to quantum transport which fully retains the wave character of electrons. In the quantum transport regime, non local effects occur and the Kirchoff laws for impedance addition in series are not valid anymore.

More recently, it has even be possible to manipulate the quantum state of superconducting nanocircuits. This line of research which has started in 1998 has lead to spectacular experiments such as for example the demonstration of two qubit quantum algorithms or the controlled preparation of complex quantum states of an oscillator with superconducting circuit implementation of cavity QED.