We report microwave-driven photon-assisted tunneling in a suspended carbon nanotube double quantum dot. From the resonant linewidth at a temperature of 13 mK, the charge-dephasing time is determined to be ps. The linewidth is independent of driving frequency, but increases with increasing temperature. The moderate temperature dependence is inconsistent with expectations from electron-phonon coupling alone, but consistent with charge noise arising in the device. The extracted level of charge noise is comparable with that expected from previous measurements of a valley-spin qubit, where it was hypothesized to be the main cause of qubit decoherence. Our results suggest a possible route towards improved valley-spin qubits.
Mavalankar, A., Pei, T., Gauger, E., Warner, J., Briggs, A., & Laird, E. (2016). Photon-assisted tunneling and charge dephasing in a carbon nanotube double quantum dot. Physical Review B, 93(23), . https://doi.org/10.1103/PhysRevB.93.235428