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Abstract: We study exchange coupling in Si double quantum dots, which have beenproposed as suitable candidates for spin qubits due to their long spincoherence times. We discuss in detail two alternative schemes which have beenproposed for implementing spin qubits in quantum dots. One scheme uses spinstates in a single dot and the interdot exchange coupling controls interactionsbetween unbiased dots. The other scheme employs the singlet and triplet statesof a biased double dot as the two-level system making up the qubit and exchangecontrols the energy splitting of the levels. Exchange in these twoconfigurations depends differently on system parameters. Our work relies on theHeitler-London approximation and the Hund-Mulliken molecular orbital method.The results we obtain enable us to investigate the sensitivity of the system tobackground charge fluctuations and determine the conditions under which optimalspots, at which the influence of the charge noise is minimized, may exist in Sidouble quantum dot structures.



Author: Qiuzi Li, Lukasz Cywinski, Dimitrie Culcer, Xuedong Hu, S. Das Sarma

Source: https://arxiv.org/



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