Mixed coupling for dispersive shift cancellation, part 1

Engineered couplings between qubits and oscillators are important to many quantum computing platforms. These couplings are largely simple dipole couplings, which limit the form 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 develop more fully the 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.