Quantum Entanglement and Coherence of Electronic States in Nanoscale Devices

摘要

Recently, a consensus has been gradually emerging that solid state nanoscale systems may eventually become the most promising prototypes of the future quantum information devices. In a solid state environment, however, the electron correlations are ubiquitous, and often they can not be neglected by any means. Nevertheless, the continuing studies (including those carried out in the framework of this project) have indicated that, instead of being an annoying nuisance to be rid of, the unavoidable interactions in nanoscale systems and the concomitant many-body effects may provide for the new opportunities for constructing novel types of qubits which% can enjoy a high degree of intrinsic coherence due to the strongly correlated nature of the underlying many-electron states. For one, in the presence of a spin-orbit coupling in a conducting crystal which renders spin a non- conserving quantum number, one may consider the still conserved total electron angular momentum J = L + S as a better candidate for a robust qubit. Also, considering the difficulty of populating a realistic quantum dot with a single electron, a better chance for constructing a quantum dot-based spin qubit might be offered by the correlated states of an reasonably large (yet, odd) number of electrons.