STIC: Development of a System of Nonlocally Interconnected Spin Qubits for Quantum Computation.

摘要

For spin-based quantum information, the period covered by STIC funding, 2005 to 2010, was one of particularly rapid advancement. At the beginning of the grant, a major breakthrough, the measurement of spin echo of a singlet-triplet spin qubit by Petta, et al. was realized (1). This development justified a major refocussing of the grant toward extending these results. The original proposal was substantially revised, and the revisions accepted by ARO. Besides a refocussing of research goals, there was a change in personnel, with the addition of Amir Yacoby as a co-PI. This occurred because Yacoby accepted a faculty position at Harvard after participating in the research leading to Refs. 1, (2). He established his own group on related topics. Over the course of the grant, four significant developments occurred, two theoretical and two experimental. The two major theoretical accomplishment were: (i) The formulation of a complete, fault-tolerant design for a quantum computer based on the singlet-triplet qubit, using measured performance parameters to evaluate fault tolerance (3). The scheme laid out in Ref. (3) continues to be the standard for the extension of singlet-triplet spin qubits into multi-qubit systems. (ii) A detailed theoretical analysis of the influence of hyperfine coupling combined with electrical (gate) noise on the performance of the singlet-triplet qubit (4). This paper emphasizes a key property of the hyperfine coupling, which is the long time scale on which it evolves compared to gate operation time. The slow dynamics of the hyperfine coupling allows coherence to be preserved using a variety of dynamical decoupling schemes.