We consider a quantum-gate mechanism based on electron spins in coupled semiconductor quantum dots. Such gates provide a general source of spin entanglement and can be used for quantum computers. We determine the exchange coupling $J$ in the effective Heisenberg model as a function of magnetic $(B)$ and electric fields, and of the interdot distance $a$ within the Heitler-London approximation of molecular physics. This result is refined by using $\mathrm{sp}$ hybridization, and by the Hund-Mulliken molecular-orbit approach, which leads to an extended Hubbard description for the two-dot system that shows a remarkable dependence on $B$ and $a$ due to the long-range Coulomb interaction. We find that the exchange $J$ changes sign at a finite field (leading to a pronounced jump in the magnetization) and then decays exponentially. The magnetization and the spin susceptibilities of the coupled dots are calculated. We show that the dephasing due to nuclear spins in GaAs can be strongly suppressed by dynamical nuclear-spin polarization and/or by magnetic fields.We consider a quantum-gate mechanism based on electron spins in coupled semiconductor quantum dots. Such gates provide a general source of spin entanglement and can be used for quantum computers. We determine the exchange coupling $J$ in the effective Heisenberg model as a function of magnetic $(B)$ and electric fields, and of the interdot distance $a$ within the Heitler-London approximation of molecular physics. This result is refined by using $\mathrm{sp}$ hybridization, and by the Hund-Mulliken molecular-orbit approach, which leads to an extended Hubbard description for the two-dot system that shows a remarkable dependence on $B$ and $a$ due to the long-range Coulomb interaction. We find that the exchange $J$ changes sign at a finite field (leading to a pronounced jump in the magnetization) and then decays exponentially. The magnetization and the spin susceptibilities of the coupled dots are calculated. We show that the dephasing due to nuclear spins in GaAs can be strongly suppressed by dynamical nuclear-spin polarization and/or by magnetic fields.

arXiv:cond-mat/9808026Physical review. B, Condensed matterJan 15, 19991,476 citations

Exchange coupling between two electrons in double quantum dot structures

Dmitriy V. Melnikov, Lu Zhang, Jean‐Pierre Leburton

Current Opinion in Solid State and Materials ScienceApr 1, 20062 citations

Spin swap and exchange coupling in a quantum dot array

M. L. de Leeuw den Bouter

Jul 9, 20140 citations

Spin and angular momentum transitions in few-electron quantum dots and rings

Ning Yang, Zhensheng Dai, Jia‐Lin Zhu

The studies on quantum dots and rings containing $4\ensuremath{\sim}6$ electrons reveal that the shapes of the systems have great impact on the spin transitions of the ground states. For five-electron case, the different shapes lead to the different transition processes in quantum dots and rings. For six-electron case, the ring confinement forbids the spin transition, which really exists in dot confinement. The investigations on the angular momentum transitions in magnetic fields show that the sensibility of the transitions to the size of the system depends remarkably on the particle number. The four-electron case is almost size insensitive but the five-electron case has obvious size dependence. It is also found that the behaviors of the few-electron entanglement in quantum dots and rings are quite different. The entanglement entropies in quantum dots increase with the increase in the magnetic field but exhibit Aharonov-Bohm oscillation patterns in narrow rings. The studies of the shape, size, and particle number effects are important for understanding the liquid-to-crystal transitions, and may be helpful for the manipulation of electronic states in quantum dots and rings.The studies on quantum dots and rings containing $4\ensuremath{\sim}6$ electrons reveal that the shapes of the systems have great impact on the spin transitions of the ground states. For five-electron case, the different shapes lead to the different transition processes in quantum dots and rings. For six-electron case, the ring confinement forbids the spin transition, which really exists in dot confinement. The investigations on the angular momentum transitions in magnetic fields show that the sensibility of the transitions to the size of the system depends remarkably on the particle number. The four-electron case is almost size insensitive but the five-electron case has obvious size dependence. It is also found that the behaviors of the few-electron entanglement in quantum dots and rings are quite different. The entanglement entropies in quantum dots increase with the increase in the magnetic field but exhibit Aharonov-Bohm oscillation patterns in narrow rings. The studies of the shape, size, and particle number effects are important for understanding the liquid-to-crystal transitions, and may be helpful for the manipulation of electronic states in quantum dots and rings.

Physical Review BJun 23, 200811 citations

Four-electron quantum dot molecule in a magnetic field

Shalva M. Tsiklauri, Roman Ya. Kezerashvili

Bulletin of the American Physical SocietyMay 28, 20080 citations

J

in the effective Heisenberg model as a function of magnetic

(B)

and electric fields, and of the interdot distance

a

within the Heitler-London approximation of molecular physics. This result is refined by using

\mathrm{sp}

hybridization, and by the Hund-Mulliken molecular-orbit approach, which leads to an extended Hubbard description for the two-dot system that shows a remarkable dependence on

B

and

a

due to the long-range Coulomb interaction. We find that the exchange

J

changes sign at a finite field (leading to a pronounced jump in the magnetization) and then decays exponentially. The magnetization and the spin susceptibilities of the coupled dots are calculated. We show that the dephasing due to nuclear spins in GaAs can be strongly suppressed by dynamical nuclear-spin polarization and/or by magnetic fields.