Carbon nanotube based nanomechanical qubit
This proposal outlines our vision for generating the first mechanical quantum bit (qubit) ever produced. The qubit will be realized with a carbon nanotube (CNT) in two steps. First, a carbon nanotube mechanical resonator is prepared in its quantum ground state and strongly coupled to an embedded electronic two-level system (eTLS). The eTLS is realized by carefully tuning the energy states of two spatially distinct charge quantum dots until they hybridize. This double quantum dot is hosted along the suspended carbon nanotube and localized such that it couples strongly to a high mechanical quality factor vibrational mode. 

Secondly, the strong coupling between the emergent eTLS and the CNT mechanical mode enables a tunable and strong anharmonicity in the mechanical restoring potential. This anharmonicity makes it possible to use the system as a qubit, which will be realized by integrating the nano-electromechanical (NEMS) device with a superconducting microwave cavity. This allows for the mechanical qubit to be coherently addressed and sensitively read-out using the state-dependent frequency shift imparted by the qubit on the superconducting cavity.