Regensburg 2004 – scientific programme
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TT: Tiefe Temperaturen
TT 22: Quantenkoh
ärenz und Quanteninformationssysteme I
TT 22.5: Talk
Wednesday, March 10, 2004, 15:30–15:45, H19
Quantum trajectory approach to the dynamics of spin qubits in quantum dots — •Holger Schaefers and Walter T. Strunz — Physikalisches Institut, Albert-Ludwigs-Universität Freiburg, Hermann-Herder-Str. 3, 79104 Freiburg, Germany
We investigate continuous measurement of a single electron spin qubit in a quantum dot as described in [1]. The dot is coupled to two leads and we choose the sequential tunneling regime. Our approach is based on quantum trajectories, widely used in quantum optics, here adapted to describe conditional quantum dot dynamics in a fermionic environment. We use the quantum trajectory approach to simulate the quantum dynamics conditioned on the continuous measurement outcome, here the electron current through the dot. We simulate so called shelving experiments and show that it is possible to measure directly the relaxation time T1, in the time domain. In a modified parameter regime the decoherence time T2 can be obtained as well. Further, using realistic parameters, we calculate counting statistics of electrons tunneling through the dot and show, that this device can be used to measure initial coherences of the qubit state.
[1] H.-A. Engel, D. Loss, Phys. Rev. Lett. 86, 4648 (2001)