Initialization and read-out of spins in coupled core–shell quantum dots

In the field of quantum information science, semiconductor quantum dots (QDs) are of particular interest for their ability to confine a single electron for use as a qubit1,2. However, to realize the potential offered by quantum information processing, it is necessary to couple two or more qubits. In contrast to coupling individual QDs, we demonstrate the integration of two coupled electronic states within a single QD heterostructure. These chemically synthesized nanocrystals, known as quantum-dot quantum wells (QDQWs)3,4,5,6,7, comprise concentric layers of different semiconducting materials. We investigate carrier and spin dynamics in these structures using transient absorption and time-resolved Faraday rotation measurements. By tuning the excitation and probe energies, we find that we can selectively initialize and read out spins in different coupled states within the QDQW. These results open a pathway for engineering coupled qubits within a single nanostructure.