Mixed coupling for dispersive shift cancellation, part 2

Engineered couplings between qubits and oscillators are important to many quantum computing platforms. These couplings are usually a single type of bilinear coupling, which limits the forms of the Hamiltonian that can be engineered. In the first talk of a two-part presentation, we discuss how mixing position-dipole coupling with momentum-dipole coupling can achieve two regimes desirable for different applications: one in which the dispersive shift is zero, and one in which the dispersive Kerr interaction is zero. We will then describe a toy model showing how superconducting circuits can achieve such mixed coupling. In the second talk, we will motivate a nonlinear readout scheme utilizing the dispersive Kerr coupling – with simulations we show how this readout scheme gives high signal-to-noise ratio while suppressing qubit dephasing into the resonator. Finally, we will show how the fluxonium molecule qubit can be a realistic instantiation for this mixed coupling concept.