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Jeudi 22 Mai 2014, 14h
Amphi Holweck, Esc C, 1ème etage
Quantum shot noise in a tunnel junction (Toward the dynamical control of tunneling processes)
Julien Gabelli
LPS, Orsay
In the presence of time dependent potentials, the natural elementary excitations of mesoscopic conductors are coherent electron-hole pairs. This can be probed by noise measurement. We experimentally demonstrate that it is possible to control the quantum noise of a tunnel junction by shaping a time-dependent drive with harmonics at frequencies f and 2f. We observe that the noise depends not only on the amplitude of the two sine waves but also on their relative phase, due to coherent emission/absorption of photons at different frequencies. By shaping the excitation we can minimize the noise of the junction, which no longer reaches its minimum at zero dc bias. We show that adding an excitation at frequency 2f with the proper amplitude and phase can reduce the noise of the junction excited at frequency f only. More precisely, we show that the quantum noise is lower by adding the excitation at frequency 2f. Varying the shape and the amplitude of the drive enables tailoring of non-equilibrium electronic distribution function and could lead to dynamic control of elementary excitations.