Dresden 2006 – scientific programme
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PV: Plenarvorträge
PV IX
PV IX: Plenary Talk
Wednesday, March 29, 2006, 09:15–10:00, HSZ 01
Coherent Control and Manipulation of Two-Electron Spin States — •Amir Yacoby — Weizmann Institute of Science, Rehovot, Israel
Entanglement is a fundamental property of quantum mechanics that is recently being harnessed to dramatically improve the acquisition, transmission, and processing of information. Dephasing in mesoscopic systems is intimately connected to entanglement whereby electrons, through unwanted interactions, become entangled with other degrees of freedom such as other electrons or phonons and loose phase coherence. To further the progress in quantum information sciences one must therefore devise ways to generate, control, and manipulate entangled states.
In this talk I shall describe our recent experiments that demonstrate coherent control of two-electron spin states in a double quantum dot allowing state preparation, coherent manipulation, and projective read-out. These techniques are based on rapid electrical control of the exchange interaction. Separating and later recombining a singlet spin state provides a measurement of the spin dephasing time, T2*∼ 10 ns, limited by hyperfine interactions with the GaAs host nuclei. Using the inevitably present nuclear hyperfine field gradients we demonstrate controlled swap operation between the |↑↓⟩ and |↓↑⟩ spin states. Spin-echo pulse sequences are used to suppress hyperfine-induced dephasing. Using these quantum control techniques, a coherence time for two-electron spin states exceeding 1 µs is observed.