Quantum computation with two-electron spins in semi-conductor quantum dots

弘理 笹倉

Cyrus C. Y. Lin, Chopin Soo, Yin‐Zhong Wu +1 more

Using electrostatic gates to control the electron positions, we present a new controlled-NOT gate based on quantum dots. The qubit states are chosen to be the spin states of an excess conductor electron in the quantum dot; and the main ingredients of our scheme are the superpositions of space-time paths of electrons and the effect of Coulomb blockade. All operations are performed only on individual quantum dots and are based on fundamental interactions. Without resorting to spin-spin terms or other assumed interactions, the scheme can be realized with a dedicated circuit and a necessary number of quantum dots. Gate fidelity of the quantum computation is also presented.

Daniel Loss

Dibyendu Roy

We study two simple mesoscopic models of interacting two electrons; first one consists of two quantum coherent parallel conductors with long-range Coulomb interaction in some localized region and the other is of an interacting quantum dot (QD) side-coupled to a noninteracting quantum wire. We evaluate exact two-particle scattering matrix as well as two-particle current which are relevant in a two-particle scattering experiment in these models. Finally we show that the on-site repulsive interaction in the QD filters out the spin-singlet two-electron state from the mixed two-electron input states in the side-coupled QD model.

Gordey B. Lesovik, A. V. Lebedev, Vladimir Lebedev +1 more

In this article we discuss our two recent proposals on producing and detecting of entangled states in quantum conductors. First we analyze a setup where two electrons are scattered on a quantum dot with Coulomb repulsion and became orbitally entangled. Second, for identical noninteracting particles we suggest an operating scheme for the deliberate generation of spin‐entangled electron pairs in a normal‐metal mesoscopic structure with a fork geometry. The spin‐entangled pair is created through a post‐selection in the two branches of the fork. We also make comments on different ways of producing and quantifying the degree of entanglement.

Li, Hai-Ou, Yao +4 more