Regensburg 2013 – wissenschaftliches Programm
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HL: Fachverband Halbleiterphysik
HL 11: Quantum information systems: mostly quantum dots
HL 11.4: Vortrag
Montag, 11. März 2013, 12:45–13:00, H16
Characterization of S-T+ qubit dynamics via correlation functions — •Christian Dickel1, 2 and Hendrik Bluhm1,2 — 12nd Institute of Physics C, RWTH Aachen University, Aachen, Germany — 2JARA - Fundamentals of Future Information Technology
Semiconductor spin qubits encoded in the singlet state S and the m=0 triplet state T0 of two electrons in a double quantum dot (DQD) have been pursued very successfully. GaAs is the most advanced material in this context, but it suffers from dephasing due to the hyperfine interaction. Recently the alternative encoding in S-T+ has been explored. For the control of such an S-T+ qubit, the dynamics at the S-T+ transition are crucial. They are driven by hyperfine coupling and spin-orbit interaction.
Here we show, through experiment and theory, that these dynamics can be probed by measuring temporal correlations of the flip probabilities during Landau-Zener-Stückelberg transitions. Those correlation functions reveal oscillations originating from the relative Lamor precession of the different nuclear species present in GaAs. Incoherent nuclear spin evolution results in a loss of correlations. In the presence of spin-orbit coupling, oscillations with the absolute Lamor frequencies are expected in addition. Observations of the latter could be useful to quantify the spin-orbit coupling in DQDs.