APS -APS March Meeting 2017 - Event - Atomically precise control of a coupled donor-quantum dot system in silicon

摘要

Single donors in silicon have long spin coherence times of interest for quantum computing. While quantum dots are promising candidates to couple donor spin qubits[1,2], the experimental tunability of the interactions and the influence of valley degrees of freedom (recently measured in donors[3]) in donor-quantum dot coupling remain open questions. We have directly measured the spectrum and wavefunctions of a donor interacting with a single-electron quantum dot that follows a movable scanned probe tip with sub-nm accuracy. Analysis of the two-electron energy as a function of the quantum dot position reveals no detectable lattice-incommensurate ``exchange oscillations'', even though donor state and its valley population is robust to quantum dot potential. This contrasts direct donor-donor exchange, which is predicted to depend sensitively on donor position due to valley interference. This result has important implications for obtaining robust interactions among donors in a surface code quantum computer.[1] G Pica et al, Phys. Rev. B. 93, 035306 (2016).[2] Gonzalez-Zalba, Phys. Rev. X 5 031024 (2015).[3] Salfi et al, Nature Materials, 13, 606 (2014).[4] B. Koiller et al, Phys. Rev. Lett. 88, 027903 (2001).