  In this letter we present an experimental realization of the quantum
mechanics textbook example of two interacting electronic quantum states that
hybridize forming a molecular state. In our particular realization, the quantum
states themselves are fabricated as quantum dots in a molecule, a carbon
nanotube.
  For sufficient quantum-mechanical interaction (tunnel coupling) between the
two quantum states, the molecular wavefunction is a superposition of the two
isolated (dot) wavefunctions. As a result, the electron becomes delocalized and
a covalent bond forms.
  In this work, we show that electrical transport can be used as a sensitive
probe to measure the relative weight of the two components in the superposition
state as a function of the gate-voltages.
  For the field of carbon nanotube double quantum dots, the findings represent
an additional step towards the engineering of quantum states.
