Excited-state spectroscopy of a quantum dot hybrid qubit via modulated longitudinal coupling to a 3D-integrated resonator

Coupling semiconductor quantum dot qubits to superconducting resonators enables reduced- control line readout and long-distance qubit interaction [1-4]. Such functionality relies on electron-photon coupling which is typically thought to be dominated by a transverse Hamiltonian term. Readout via transverse resonator coupling has been extensively studied for both semiconducting and superconducting qubits; however, there exist other coupling mechanisms that affect qubit-resonator interaction under certain operating regimes [5-6]. Here, we demonstrate enhanced transmission through a 3D-integrated TiN resonator coupled to a Si/SiGe quantum dot hybrid qubit by modulating double-dot detuning at the resonator frequency. We attribute the boosted signal to a dynamical longitudinal coupling term in the qubit-resonator Hamiltonian. We perform pulsed spectroscopy of the qubit states, demonstrating that dynamical longitudinal coupling can be a powerful tool for resonator-qubit readout.

 

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[2] X. Mi et al. Nature 555, 599 (2018).

[3] F. Borjans et al. Nature 577, 195 (2020).

[4] N. Holman et al. npj Quantum Inf. 7, 137 (2021). 

[5] A. J. Kerman. New J. Phys. 15, 123011 (2013).

[6] R. Ruskov and C. Tahan. Phys. Rev. B 99, 245306 (2019).