Conduction of Ultracold Fermions Through a Mesoscopic Channel

In a mesoscopic conductor electric resistance is detected even if the device is defect-free. We engineer and study a cold-atom analog of a mesoscopic conductor. It consists of a narrow channel connecting two macroscopic reservoirs of fermions that can be switched from ballistic to diffusive. We induce a current through the channel and find ohmic conduction, even for a ballistic channel. An analysis of in-situ density distributions shows that in the ballistic case the dissipation is localized at the entrance and exit of the channel, revealing the presence of contact resistance. In contrast, a diffusive channel with disorder displays dissipation over the whole channel. Our approach opens the way towards quantum simulation of mesoscopic devices with quantum gases.