Observation of "Partial Coherence" in an Aharonov-Bohm Interferometer with a Quantum Dot

We report experiments on the interference through spin states of electrons in a quantum dot (QD) embedded in an Aharonov-Bohm (AB) interferometer. We have picked up a spin-pair state, for which the environmental conditions are ideally similar and have traced the AB amplitude in the range of the gate voltage that covers the pair. The behavior of the asymmetry in the amplitude around the two Coulomb peaks agrees with the theoretical prediction that relates a spin-flip process in a QD to the quantum dephasing of electrons. These results consist evidence of "partial coherence" due to an entanglement of spins in the QD and the interferometer.