The relentless scaling of electronic devices have led to a regime where the device operation is dictated by only a small number atoms in the active region. The new emerging areas of research such as spintronics, valleytronics, and solotronics, demand an understanding and control of quantum physics at single atom level, both in real and momentum space. In this talk, I shall present our theoretical work on single impurity atoms in semiconductors based on multi-million-atom tight-binding simulations. The spatially resolved imaging of electron wave functions confined on individual impurity atoms via low temperature scanning tunnelling microscope (STM) measurements has allowed to understand and benchmark the underpinning quantum physics with ultimate precision. By coupling large-scale atomistic wave function simulations with the Bardeen’s tunnelling formalism, we have been able to compute STM images with an unprecedented accuracy, leading to the world’s first spatial metrology of impurities in silicon with single atom precision. The direct visualisation of two-particle correlated states provides a unique tool to understand and engineer exchange interaction between dopant atoms, a crucial component in the designing of two-qubit quantum gates. A scalable quantum computer architecture is proposed incorporating fast exchange interaction and surface code error correction scheme. In the final part of my talk, I will discuss some recent ongoing work on spin qubits as platform for magnetic resonance imaging of single molecules and engineering 2D materials for topological electronic states