Photon-assisted tunneling and charge dephasing in a carbon nanotube double quantum dot

TL;DR

This study demonstrates microwave-induced photon-assisted tunneling in a suspended carbon nanotube double quantum dot, revealing charge dephasing characteristics and suggesting pathways to enhance valley-spin qubit coherence.

Contribution

The paper provides the first measurement of charge dephasing time in a carbon nanotube double quantum dot using photon-assisted tunneling.

Findings

Charge dephasing time is approximately 280 ps.

Linewidth increases with temperature but is independent of driving frequency.

Charge noise levels are comparable to those affecting valley-spin qubits.

Abstract

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 280 +- 30 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.