### Abstract

We theoretically study the electronic states and spin operation in coupled quantum dots, based on the calculations of many-body wavefunctions. We adopt a tight-binding model on a square lattice with a smooth tunnel barrier around its center. Taking into account the electron-electron interaction by the exact diagonalization method, we evaluate the spin coupling J between two electron spins, as a function of magnetic field perpendicular to the quantum dots, and show a transition from antiferromagnetic coupling (J > 0) to ferromagnetic coupling (J < 0). The coupling J is not seriously influenced by the size difference between the dots if the energy levels are tuned to match each other using the gate voltage. Next, we simulate SWAP gate operation by calculating the time development of two electron spins. A nonadiabatic change of the tunnel barrier between the quantum dots may cause operation errors, due to the contribution from high energy states. The complete exchange of the spin states could be also blocked by the spin-orbit interaction.

Original language | English |
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Title of host publication | MS+S 2006 - Controllable Quantum States: Mesoscopic Superconductivity and Spintronics, Proceedings of the International Symposium |

Publisher | World Scientific Publishing Co. Pte Ltd |

Pages | 239-244 |

Number of pages | 6 |

ISBN (Print) | 9812814612, 9789812814616 |

Publication status | Published - 2008 |

Event | 4th International Symposium on Mesoscopic Superconductivity and Spintronics, MS+S 2006 - Atsugi, Japan Duration: 2006 Feb 27 → 2006 Mar 2 |

### Other

Other | 4th International Symposium on Mesoscopic Superconductivity and Spintronics, MS+S 2006 |
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Country | Japan |

City | Atsugi |

Period | 06/2/27 → 06/3/2 |

### Fingerprint

### ASJC Scopus subject areas

- Electrical and Electronic Engineering

### Cite this

*MS+S 2006 - Controllable Quantum States: Mesoscopic Superconductivity and Spintronics, Proceedings of the International Symposium*(pp. 239-244). World Scientific Publishing Co. Pte Ltd.

**Theoretical study of electronic states and spin operation in coupled quantum dots.** / Goto, D.; Eto, Mikio.

Research output: Chapter in Book/Report/Conference proceeding › Conference contribution

*MS+S 2006 - Controllable Quantum States: Mesoscopic Superconductivity and Spintronics, Proceedings of the International Symposium.*World Scientific Publishing Co. Pte Ltd, pp. 239-244, 4th International Symposium on Mesoscopic Superconductivity and Spintronics, MS+S 2006, Atsugi, Japan, 06/2/27.

}

TY - GEN

T1 - Theoretical study of electronic states and spin operation in coupled quantum dots

AU - Goto, D.

AU - Eto, Mikio

PY - 2008

Y1 - 2008

N2 - We theoretically study the electronic states and spin operation in coupled quantum dots, based on the calculations of many-body wavefunctions. We adopt a tight-binding model on a square lattice with a smooth tunnel barrier around its center. Taking into account the electron-electron interaction by the exact diagonalization method, we evaluate the spin coupling J between two electron spins, as a function of magnetic field perpendicular to the quantum dots, and show a transition from antiferromagnetic coupling (J > 0) to ferromagnetic coupling (J < 0). The coupling J is not seriously influenced by the size difference between the dots if the energy levels are tuned to match each other using the gate voltage. Next, we simulate SWAP gate operation by calculating the time development of two electron spins. A nonadiabatic change of the tunnel barrier between the quantum dots may cause operation errors, due to the contribution from high energy states. The complete exchange of the spin states could be also blocked by the spin-orbit interaction.

AB - We theoretically study the electronic states and spin operation in coupled quantum dots, based on the calculations of many-body wavefunctions. We adopt a tight-binding model on a square lattice with a smooth tunnel barrier around its center. Taking into account the electron-electron interaction by the exact diagonalization method, we evaluate the spin coupling J between two electron spins, as a function of magnetic field perpendicular to the quantum dots, and show a transition from antiferromagnetic coupling (J > 0) to ferromagnetic coupling (J < 0). The coupling J is not seriously influenced by the size difference between the dots if the energy levels are tuned to match each other using the gate voltage. Next, we simulate SWAP gate operation by calculating the time development of two electron spins. A nonadiabatic change of the tunnel barrier between the quantum dots may cause operation errors, due to the contribution from high energy states. The complete exchange of the spin states could be also blocked by the spin-orbit interaction.

UR - http://www.scopus.com/inward/record.url?scp=84903900855&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=84903900855&partnerID=8YFLogxK

M3 - Conference contribution

AN - SCOPUS:84903900855

SN - 9812814612

SN - 9789812814616

SP - 239

EP - 244

BT - MS+S 2006 - Controllable Quantum States: Mesoscopic Superconductivity and Spintronics, Proceedings of the International Symposium

PB - World Scientific Publishing Co. Pte Ltd

ER -