  We present a technique for integrating ultraclean carbon nanotubes into
superconducting circuits, aiming to realize Josephson junctions based on
one-dimensional elementary quantum conductors. This technique primarily
involves depositing the nanotube in the final step, thus preserving it from the
inherent contaminations of nanofabrication and maintaining contact solely with
superconducting electrodes and a crystalline hBN substrate. Through transport
measurements performed in both the normal and superconducting states, we
demonstrate that our method yields high-quality junctions with Josephson
energies suitable for quantum device applications, such as carbon
nanotube-based superconducting qubits.
