Coulomb interaction energy in optical and quantum computing applications of self-assembled quantum dots

Electrons and holes confined in semiconductor quantum dots are affected energetically by Coulomb charge interactions. In this work, the influence of Coulomb interactions is considered for optical and quantum computing applications of quantum dots. For example, the operating frequencies of photoemitters and detectors depend on these transition energies, and some proposed charge-based quantum computing devices use these interactions to identify the binary state of a quantum qubit. To study these applications, the energy changes due to Coulomb attraction-repulsion effects are calculated here and compared with the transition energies for states confined in a single dot or occupying different, neighboring dots. The exciton binding energies for states within the same dot are non-negligible, even for large dots. The importance of this conclusion for quantum dot optical applications is discussed. Conversely, for realistic self-assembled lateral arrays of quantum dots, it is shown that the energy of charge interactions between neighboring dots is not high enough to be measured in practice. The difficulty that this poses for proposed charge-based quantum computing applications is discussed.