Ultra-dispersive Resonator Readout of a Quantum-Dot Qubit Using Longitudinal Coupling

We perform readout of a quantum-dot hybrid qubit coupled to a superconducting resonator through a parametric, longitudinal interaction mechanism. Our experiments are performed with the qubit and resonator frequencies detuned by ∼10 GHz, demonstrating that longitudinal coupling can facilitate semiconductor qubit operation in the 'ultra-dispersive' regime of circuit quantum electrodynamics.