Coherent Control of a Carbon Nanotube Mechanical Mode and implications for Spin-based Quantum Devices (Part 1)

We demonstrate coherent control of a suspended carbon nanotube mechanical mode (99 MHz) embedded in a cQED architecture. The mechanical mode couples to the electronic orbital states of a double quantum dot formed in the nanotube, giving rise to a hybridized orbital-mechanical system. The degree of hybridization is tunable through gate-controlled electric fields. The mechanical mode is driven electrically via a nearby gate electrode, and state readout is performed dispersively using a superconducting resonator coupled to the orbital degree of freedom.

In part 1 of this talk, we present our orbital-mechanical platform and demonstrate quantum oscillations of the hybridized system. These measurements reveal weak anharmonicity, placing the system outside the typical qubit regime while still enabling coherent manipulation. Characterizing the orbital-mechanical coupling provides insight into a key decoherence pathway for carbon nanotube spin qubits: spin decoherence via orbital states into mechanical modes. We discuss these results in the context of a proposed CNT-based flopping mode spin qubit.