K. M. Weiss, J. M. Elzerman, Y. L. Delley, J. Miguel-Sanchez, A. Imamoglu
In semiconductors, the T2* coherence time of a single confined spin is limited either by the fluctuating magnetic environment (via the hyperfine interaction), or by charge fluctuations (via the spin-orbit interaction). We demonstrate that both limitations can be overcome simultaneously by using two exchange-coupled electron spins that realize a single decoherence-avoiding qubit. Using coherent population trapping, we generate a coherent superposition of the singlet and triplet states of an optically active quantum-dot molecule, and show that the corresponding T2* may exceed 200 nanoseconds.
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http://arxiv.org/abs/1112.4710
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