Nonadiabatic quantum control of a semiconductor charge qubit
  We demonstrate multipulse quantum control of a single electron charge qubit. The qubit is manipulated by applying nonadiabatic voltage pulses to a surface depletion gate and readout is achieved using a quantum point contact charge sensor. We observe Ramsey fringes in the excited state occupation in response to a pi/2 - pi/2 pulse sequence and extract T2* ~ 60 ps away from the charge degeneracy point. Simulations suggest these results may be extended to implement a charge-echo by reducing the interdot tunnel coupling and pulse rise time, thereby increasing the nonadiabaticity of the pulses. 
Y. Dovzhenko, J. Stehlik, K. D. Petersson, J. R. Petta, H. Lu, and A.   C. Gossard
cond-mat.mes-hall quant-ph