We demonstrate the parametric modulation of a double quantum dot charge dipole coupled to a cavity, at the cavity frequency, achieving an amplified readout signal compared to conventional dispersive protocols. Our findings show that the observed cavity field displacement originates from dipole radiation within the cavity, rather than from a longitudinal coupling mechanism, yet exhibits the same signatures while relying on a transverse coupling. By carefully tuning the phase and amplitude of the intracavity field, we achieve a $\pi$-phase shift between two dipole states, resulting in a substantial enhancement of the signal-to-noise ratio. In addition to its applications in quantum dot based qubits in circuit QED architectures, this protocol could serve as a new promising tool for probing exotic electronic states in mesoscopic circuits embedded in cavities.

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• Circuit quantum electrodynamics
• Electrical properties
• Quantum information with solid state qubits
• Double quantum dots
• Nanotubes