Regensburg 2019 – wissenschaftliches Programm

Bereiche | Tage | Auswahl | Suche | Aktualisierungen | Downloads | Hilfe

TT: Fachverband Tiefe Temperaturen

TT 40: Superconductivity: Qubits 1

TT 40.7: Vortrag

Mittwoch, 3. April 2019, 11:00–11:15, H48

Dispersive Readout of AC-Driven Qubits — •Sigmund Kohler — Instituto de Ciencia de Materiales de Madrid, CSIC

We present a unified picture of dispersive readout of quantum systems in and out of equilibrium. A cornerstone of the approach is the backaction of the measured system to the cavity obtained with non-equilibrium linear response theory. It provides the dispersive shift of the cavity frequency in terms of a system susceptibility [1] as well as resonance conditions that relate the cavity transmission to spectral properties and Berry phases [2]. Examples are the readout of detuned qubits and thermally excited multi-level systems. For ac-driven quantum systems, we identify the relevant Fourier component of the susceptibility and introduce a computational scheme based on Floquet theory. The theory is applied to Landau-Zener-Stückelberg-Majorana interference in Si/SiGe double quantum dots, where the interference patterns exhibit a harp-like stemming from the valley degree of freedom [3]. The theoretical and experimental interference patterns show a striking agreement.

[1] S. Kohler, Phys. Rev. A 98, 023849 (2018).

[2] S. Kohler, Phys. Rev. Lett. 119, 196802 (2017).

[3] X. Mi, S. Kohler, J. R. Petta, Phys. Rev. B 98, 161404(R) (2018).