Enhancing the coherence of a spin qubit by operating it as a feedback loop that controls its nuclear spin bath |
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Authors: | Bluhm Hendrik Foletti Sandra Mahalu Diana Umansky Vladimir Yacoby Amir |
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Institution: | Department of Physics, Harvard University, Cambridge, Massachusetts 02138, USA. |
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Abstract: | 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 tenfold increase in the inhomogeneous dephasing time T?* 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. |
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