  In transport experiments the quantum nature of matter becomes directly
evident when changes in conductance occur only in discrete steps, with a size
determined solely by Planck's constant h. The observations of quantized steps
in the electric conductance have provided important insights into the physics
of mesoscopic systems and allowed for the development of quantum electronic
devices. Even though quantized conductance should not rely on the presence of
electric charges, it has never been observed for neutral, massive particles. In
its most fundamental form, the phenomenon requires a quantum degenerate Fermi
gas, a ballistic and adiabatic transport channel, and a constriction with
dimensions comparable to the Fermi wavelength. Here we report on the
observation of quantized conductance in the transport of neutral atoms. We
employ high resolution lithography to shape light potentials that realize
either a quantum point contact or a quantum wire for atoms. These constrictions
are imprinted on a quasi two-dimensional ballistic channel connecting two
adjustable reservoirs of quantum degenerate fermionic lithium atoms. By tuning
either a gate potential or the transverse confinement of the constrictions, we
observe distinct plateaus in the conductance for atoms. The conductance in the
first plateau is found to be equal to 1/h, the universal conductance quantum.
For low gate potentials we find good agreement between the experimental data
and the Landauer formula, with all parameters determined a priori. Our
experiment constitutes the cold atom version of a mesoscopic device and can be
readily extended to more complex geometries and interacting quantum gases.
