Regensburg 2007 – wissenschaftliches Programm
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SYEN: Symposium Entanglement
SYEN 1: Symposium Entanglement
SYEN 1.6: Hauptvortrag
Donnerstag, 29. März 2007, 16:30–17:00, H1
Sweep a qubit to learn about its environment — •Peter Hänggi1, Martijn Wubs1, Keiji Saito2, Roland Doll1, Sigmund Kohler1, and Yosuke Kayanuma3 — 1Institut für Physik, Universität Augsburg — 2University of Tokyo, Japan — 3Osaka Prefecture University, Japan
We derived the exact zero-temperature transition probability for the dissipative Landau-Zener problem. The standard (non-dissipative) Landau-Zener problem is an exactly solvable textbook example in time-dependent quantum mechanics which has found many applications in physics and chemistry. Our exact result [1] constitutes an important generalization: it describes how the coupling of the qubit to its environment changes the transition probability. Moreover, we find that the final quantum state exhibits a peculiar entanglement between the qubit and the bath. A large class of realistic types of coupling is considered. Surprisingly, the final transition probability is not affected at all by environments that only cause pure dephasing. In general, we find that Landau-Zener sweeps provide a robust tool for characterizing the environment of a tunable qubit. Promising applications include superconducting qubits, especially in circuit QED [2,3].
[1] M. Wubs et al., Phys. Rev. Lett. 97, 200404 (2006).
[2] K. Saito et al., Europhys. Lett. 76, 22 (2006).
[3] R. Doll et al., Europhys. Lett. 76, 547 (2006).