Abstract

The phase of a wave function is the most fundamental concept of quantum mechanics .Using electron electron wave interferometers, numerous numerous attempts have been made to measure and control the phase shift of an electron wave. Despite the apparent simplicity, however, no reliable phase measurement had been realized because multiple-path interference usually masks the unambiguous information of the phase. In this talk, I present a pure two-path interference that is realized by combining an Aharonov-Bohm ring with parallel tunnel-coupled quantum wires, where the phase shift can be measured and electrically controlled. We also embedded a quantum dot into one of the two paths to measure the scattering phase through an artificial atom. We have revealed influences of the parity of orbital wave function in the quantum dot and the interaction between a local spin confined in the quantum dot and conducting electrons in the reservoirs, i.e.the Kondo effect.