Far-detuned two-qubit operation of the quantum-dot hybrid qubit coupled to a microwave resonator

The quantum-dot hybrid qubit has a natural spin-charge hybridization that provides an electric dipole that can be used to perform EDSR or to couple the qubit to cavity photons. This electric-dipole moment is maximized in the charge-like regime, at small detuning, and it is reduced by going to the far-detuned regime. In this latter regime, the qubit behaves as a spin qubit, with good coherence properties, yet with a small dipolar moment.

In this work, we explore this far-detuned regime. The control parameters of the quantum-dot hybrid qubit can be adjusted to form a sweet spot in the far-detuned regime, increasing the qubit coherence times enough to allow operation with a small dipolar moment. At this sweet spot, the qubit can be strongly coupled to a superconducting resonator, allowing two-qubit gates to be performed. We find that the optimal operation of two-qubit gates, in terms of gate speed and experimental feasibility, is obtained by exploiting sideband transitions, achieving a 99% two-qubit gate fidelity in the best case.