2010/03/31 by Hendrik Bluhm, Sandra Foletti, Diana Mahalu +2 · 1 citation
Physics and Astronomy · #cond-mat.mes-hall #quant-ph
paper · pdf · doi:10.1103/physrevlett.105.216803
published as Phys. Rev. Lett. 105, 216803 (2010) · Journal version. Improved clarity of presentation and more concise terminology. 4 pages, 3 figures. Supplementary document included as ancillary file
arxiv created 2010/11/27 · arxiv updated 2010/11/30
In many realizations of electron spin qubits the dominant source of decoherence is the fluctuating nuclear spin bath of the host material. The slowness of this bath lends itself to a promising mitigation strategy where the nuclear spin bath is prepared in a narrowed state with suppressed fluctuations. Here, this approach is realized for a two-electron spin qubit in a GaAs double quantum dot and a nearly ten-fold increase in the inhomogeneous dephasing time T2^* is demonstrated. Between subsequent measurements, the bath is prepared by using the qubit as a feedback loop that first measures its nuclear environment by coherent precession, and then polarizes it depending on the final state. This procedure results in a stable fixed point at a nonzero polarization gradient between the two dots, which enables fast universal qubit control.