  A pristine suspended carbon nanotube is a near ideal environment to host
long-lived quantum states. For this reason, they have been used as the core
element of qubits and to explore numerous condensed matter physics phenomena.
One of the most advanced technique to realize complex carbon nanotube based
quantum circuits relies on a mechanical integration of the nanotube into the
circuit. Despite the high-quality and complexity of the fabricated circuits,
the range of possible experiments was limited to the closed quantum dot regime.
Here, by engineering a transparent metal-nanotube interface, we developed a
technique that overcomes this limitation. We reliably reach the open quantum
dot regime as demonstrated by measurements of Fabry-Perot interferences and
Kondo physics in multiple devices. A circuit-nanotube alignment precision of
+/-200nm is demonstrated. Our technique allows to envision experiments
requiring the combination of complex circuits and strongly coupled carbon
nanotubes such as the realization of carbon nanotube superconducting qubits or
flux-mediated optomechanics experiments.
