Multimode superconducting circuits for realizing strongly coupled multiqubit processor units
Tanay Roy, Madhavi Chand, Anirban Bhattacharjee, Sumeru Hazra, S. Kundu, Kedar Damle, Rajamani Vijay · Physical Review A · 2018
Interqubit coupling and qubit connectivity in a processor are crucial for achieving high-fidelity multiqubit gates and efficient implementation of quantum algorithms. Typical superconducting processors employ relatively weak transverse interqubit coupling which is activated via frequency tuning or microwave drives. Here, we propose a class of multimode superconducting circuits which realize multiple transmon qubits with all-to-all longitudinal coupling. These ``artificial molecules'' directly implement a multidimensional Hilbert space that can be easily manipulated due to the always-on longitudinal coupling. We describe the basic technique to analyze such circuits, compute the relevant properties, and discuss how to optimize them to create efficient small-scale quantum processors with universal programmability.