A fast tunable 3D-transmon architecture for superconducting qubit-based hybrid devices

TL;DR

This paper introduces a fast-flux line integrated into a 3D cavity architecture for superconducting transmon qubits, enabling rapid frequency tuning and improved control in hybrid quantum devices.

Contribution

It demonstrates the integration of a fast-flux line in a 3D transmon architecture, enabling quick frequency tuning and coherent control of superconducting qubits.

Findings

Achieved a resurgence time of 4.8 microseconds for coherence recovery.

Demonstrated excitation swap between cavity and qubit modes.

Estimated flux line bandwidth to be approximately 100 MHz.

Abstract

Superconducting qubits utilize the strong non-linearity of the Josephson junctions. Control over the Josephson nonlinearity, either by a current bias or by the magnetic flux, can be a valuable resource that brings tunability in the hybrid system consisting of superconducting qubits. To enable such a control, here we incorporate a fast-flux line for a frequency tunable transmon qubit in 3D cavity architecture. We investigate the flux-dependent dynamic range, relaxation from unconfined states, and the bandwidth of the flux-line. Using time-domain measurements, we probe transmon's relaxation from higher energy levels after populating the cavity with $\approx 2.1\times10^4$ photons. For the device used in the experiment, we find a resurgence time corresponding to the recovery of coherence to be 4.8~$\mu$s. We use a fast-flux line to tune the qubit frequency and demonstrate the swap of a single excitation between cavity and qubit mode. By measuring the deviation in the transferred population from the theoretical prediction, we estimate the bandwidth of the flux line to be $\approx$~100~MHz, limited by the parasitic effect in the design. These results suggest that the approach taken here to implement a fast-flux line in a 3D cavity could be helpful for the hybrid devices based on the superconducting qubit.