Fast quantum oscillations of a charge qubit in a double quantum dot fabricated in a Si/SiGe heterostructure are demonstrated and characterized experimentally. The measured inhomogeneous dephasing time T2* ranges from 127ps to ~2.1ns; it depends substantially on how the energy difference of the two qubit states varies with external voltages, consistent with a decoherence process that is dominated by detuning noise(charge noise that changes the asymmetry of the qubit's double-well potential). In the regime with the shortest T2*, applying a charge-echo pulse sequence increases the measured inhomogeneous decoherence time from 127ps to 760ps, demonstrating that low-frequency noise processes are an important dephasing mechanism.
@article{arxiv.1208.0519,
title = {Coherent Quantum Oscillations in a Silicon Charge Qubit},
author = {Zhan Shi and C. B. Simmons and Daniel. R. Ward and J. R. Prance and R. T. Mohr and Teck Seng Koh and John King Gamble and Xian. Wu and D. E. Savage and M. G. Lagally and Mark Friesen and S. N. Coppersmith and M. A. Eriksson},
journal= {arXiv preprint arXiv:1208.0519},
year = {2013}
}