Controlling ultrahigh-quality microwave resonators with noisy nonlinear circuits

Three-dimensional microwave cavity resonators can reach lifetimes of the order of a second by maximizing the cavity volume relative to its surface. Such cavities represent an ideal platform for quantum computing with bosonic qubits but their efficient control remains an outstanding problem since the large mode volume results in inefficient coupling to nonlinear elements used for their control. Moreover, this coupling introduces additional cavity decay via the inverse Purcell effect which can easily destroy the advantage of long intrinsic lifetime. In this talk, we will discuss conditions on, and protocols for, efficient control of these ultrahigh-quality microwave cavities using conventional nonlinear circuits. We will compare various schemes based on resonant and dispersive interactions of the cavity with the control element and strategies for enhancing these interactions using suitable pumping of the cavity and control circuit. Our work thus explores a potentially viable roadmap towards using ultrahigh-quality microwave cavity resonators for storing and processing information encoded in bosonic qubits.