Sub-wavelength addressing of superconducting qubits in a rectangular waveguide

Superconducting qubits coupled to microwave waveguides are a promising platform for quantum simulation. The combination of direct qubit interaction and the coupling to an open quantum system allows for a wide variety of Hamiltonians to be modeled with relatively minimal hardware. However, it can be a challenge to address individual qubits in such systems, as they are often separated by less than the wavelength of their control field. This problem can be overcome by using the non-linear dispersion of a rectangular waveguide near its cutoff frequency to self-focus a microwave pulse at a highly resolved location within the waveguide. Furthermore, such a pulse can be used to selectively control a qubit[1]. We experimentally demonstrate this control using transmon qubits embedded in a rectangular waveguide.

[1] Casulleras et al. arXiv:2005.07506