We propose a scheme for coherent rotation of the valley isospin of a single electron confined in a carbon nanotube quantum dot [1]. The scheme exploits the ubiquitous atomic disorder of the nanotube crystal lattice, which induces time-dependent valley mixing as the confined electron is pushed back and forth along the nanotube axis by an applied ac electric field. Using experimentally determined values for the disorder strength [2,3], we estimate that valley Rabi oscillations with a period on the nanosecond time scale are feasible. The valley resonance effect can be detected in the electric current through a double quantum dot in the single-electron transport regime.

[1] A. Palyi and G. Burkard, Phys. Rev. Lett. 106, 086801 (2011).
[2] F. Kuemmeth et al., Nature 452, 448 (2008).
[3] H. O. H. Churchill et al., Phys. Rev. Lett. 102, 166802 (2009).