Dispersive regime |Δ| ≫ g: qubit-state-dependent resonator frequency pull 2χ

Wallraff-Schuster-Blais 2004 dispersive-readout scheme for circuit QED. Starting from the Jaynes-Cummings Hamiltonian H_JC = ℏω_q σ_z/2 + ℏω_r a†a + ℏg(σ_+ a + σ_− a†), a Schrieffer-Wolff transformation to leading order in g/Δ (Δ ≡ ω_q −…