On-demand parametric interaction between the dipole and plasma modes of a Josephson circuit – PART 1/2

Qubits based on Josephson junctions are at the core of the most advanced superconducting quantum processors. Typically, the coupling between these qubits decreases as the detuning between their transition frequencies increases. Therefore, superconducting quantum circuits often suffer from frequency crowding, which can deteriorate the performances of driven operations. In this talk, we demonstrate a novel, hardware-efficient approach for performing on-demand photon swaps in as little as 5 ns between two transmon-like qubits with transition frequencies of 8.4 GHz and 23.8 GHz. The qubits are realized as the dipole and plasma modes, respectively, of a single flux-biased Josephson superconducting loop shunted by a capacitance, with a total footprint of approximately 0.01 mm². Our work sets the stage for the development of superconducting devices akin to Rydberg atoms, with the lower-frequency qubit acting as the protected hyperfine-structure transition, and the higher-frequency qubit acting as the strongly interacting Rydberg transition.

Part 1 will present the device theory, modeling and extraction of electrical parameters.