Coherent Electron Transport by Adiabatic Passage in an Imperfect Donor Chain
Date of this Version9-20-2010
This work was supported by the Laboratory Directed Research and Development program at Sandia National Laboratories and by the National Security Agency Laboratory for Physical Sciences under contract number EAO-09-0000049393. Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy under Contract No. DE-AC04-94AL85000. Part of the development of NEMO-3D was initially performed at JPL, Caltech under a contract with NASA. NCN/nanohub.org computational resources were used. This work was supported by the Australian Research Council, NSA and ARO (contract number W911NF-04-1-0290). A.D.G. and L.C.L.H. acknowledge the Australian Research Council for financial support (Projects No. DP0880466 and No. DP0770715, respectively). R.R. also acknowledges discussions with T. Gurrieri and R. Young of SNL.
Coherent Tunneling Adiabatic Passage (CTAP) has been proposed as a long-range physical qubit transport mechanism in solid-state quantum computing architectures. Although the mechanism can be implemented in either a chain of quantum dots or donors, a 1D chain of donors in Si is of particular interest due to the natural conﬁning potential of donors that can in principle help reduce the gate densities in solid-state quantum computing architectures. Using detailed atomistic modeling, we investigate CTAP in a more realistic triple donor system in the presence of inevitable fabrication imperfections. In particular, we investigate how an adiabatic pathway for CTAP is aﬀected by donor misplacements, and propose schemes to correct for such errors. We also investigate the sensitivity of the adiabatic path to gate voltage ﬂuctuations. The tight-binding based atomistic treatment of straggle used here may beneﬁt understanding of other donor nanostructures, such as donor-based charge and spin qubits. Finally, we derive an eﬀective 3 × 3 model of CTAP that accurately resembles the voltage tuned lowest energy states of the multi-million atom tight-binding simulations, and provides a translation between intensive atomistic Hamiltonians and simpliﬁed eﬀective Hamiltonians while retaining the relevant atomic-scale information. This method can help characterize multi-donor experimental structures quickly and accurately even in the presence of imperfections, overcoming some of the numeric intractabilities of ﬁnding optimal eigenstates for non-ideal donor placements.
Nanoscience and Nanotechnology