3D cavity-based graphene superconducting quantum circuits in two-qubit architectures

TL;DR

This paper demonstrates the integration of graphene-based superconducting quantum circuits into 3D cavities, showing tunable qubits, multiple coupling regimes, and initial steps toward multi-qubit 3D transmon devices using 2D materials.

Contribution

It introduces a novel approach to building 3D cavity-based superconducting circuits with graphene, enabling flexible coupling and multi-qubit architectures from 2D materials.

Findings

Demonstrated flux-tunable qubit transition with T1 ≈ 48 ns

Observed vacuum Rabi splitting and flux-dependent linewidths

Showed coupling between two circuits via a single cavity mode

Abstract

We construct a series of graphene-based superconducting quantum circuits and integrate them into 3D cavities. For a single-qubit device, we demonstrate flux-tunable qubit transition, with a measured $T_1$ $\approx$ 48 ns and a lower bound estimate of $T_2^\ast$ $\approx$ 17.63 ns. By coupling the device to cavities with different resonant frequencies, we access multiple qubit-cavity coupling regimes, enabling the observation of vacuum Rabi splitting and flux-dependent spectral linewidths. In a two-qubit device consisting of a SQUID and a single junction, power-dependent measurements reveal a two-stage dispersive shift. By flux-tuning the cavity frequency at different readout powers, we attribute the first shift to the fixed-qubit and the second to the SQUID-qubit, indicating successful coupling between the two circuits and a single cavity mode. Our study demonstrates the flexible coupling achievable between 2D-material-based superconducting circuits and 3D cavities, and paves the way toward constructing multi-qubit 3D transmon devices from 2D materials.