VietNam 2013 

IXth Rencontres du Vietnam
Quy-Nhon, August 4-10, 2013


 Nanophysics: from fundamentals to applications

(the return)


Monday 5
Dots and wires
Y. Gefen
› 14:00 - 14:30 (30min)
Efficient Operation of Spin Qubit Gates and Photon-spin Interface with Quantum Dots
Seigo Tarucha  2, 1@  
2 : Center for Emergent Matter Science, Riken
Tokyo -  Japan
1 : Applied Phys Dept, The University of Tokyo
Tokyo -  Japan

Semiconductor quantum dots (QDs) provide a useful platform for quantum logical operations with electron spins in quantum computing as well as quantum interface between photons and electron spins. We previously prepared a two qubit gate to control the degree of spin entanglement in the double QD. Our qubit operation is realized by electrically oscillating an electron inside the QD in the presence of a micro-magnet induced field gradient. However, the gate operation time was comparable to or longer than the dephasing time due to the fluctuating nuclear spin bath and therefore the gate fidelity was low. We have recently improved the spin rotation efficiency with the spin-flip time much shorter than the dephasing time and the gate fidelity exceeding 96\%.

 One of the prerequisites for implementing the photon to spin interface is to detect a single photon-generated electron and judge the spin orientation in a time scale smaller than the spin-flip time. We have used a double QD made in a g-factor engineered quantum well to read out the photo-electron spin using the Pauli effect after selective excitation of the heavy hole band. We have demonstrated angular momentum transfer from single photons to single electrons through single shot measurement of interdot tunneling of photo-electrons.

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