The rapid progress of miniaturization has shrunk electronic devices so much that their dimensions now become comparable to the size of atoms. Field-effect transistors with a length of the order of a few tens of nanometers are already on the market. In the laboratory, state-of-the-art nanofabrication even reaches the ultimate stage: it is possible to make individual structures consisting of a few atoms or molecules. A novel situation appears: the quantum behavior of electrons can emerge at the level of collective electrical variables described by the macroscopic concepts of voltages, currents, resistors, capacitors and so on.
It is important to note that in microelectronics, quantum mechanics only entered so far to explain material properties and did not play a role in the electrodynamics of circuits which always remained classical. What new phenomena arise when electron quantum coherence span a whole device and can influence its collective behavior? The aim of the research performed by the QUANTum physics and electrRONICS group is to answer experimentally this question. Using electron-beam lithography, low-temperature and ultra-low-noise techniques, we design, fabricate and measure metallic circuits in which quantum effects manifest themselves directly on macroscopic electrical quantities.