Fully tuneable coherence and control of acceptor qubits

2017. 07. 11. 14:15
Building F, Entrance III, seminar room of Department of Theoretical Physics
Dimi Culcer (UNSW Sydney)

Electrical control of quantum bits could pave the way for scalable quantum computation. An acceptor spin qubit in Si, based on spin-3/2 holes, can be controlled by electrical means using a gate electrode, which offers fast one- and two-qubit rotations and long coherence times at certain sweet spots. The relaxation time T1, while allowing >10^5 operations, is the primary limiting factor. I will show that, due to the interplay of the Td symmetry of the acceptor in the Si lattice and the spin-3/2 characteristic of hole systems, an applied in-plane magnetic field strongly enhances the performance and coherence properties of the qubit. An appropriate choice of magnetic field orientation leads to a near-total suppression of spin relaxation as well as full tunability of two-qubit operations in a parameter regime in which dephasing due to charge fluctuations can be eliminated. Interestingly for spintronic applications, an extreme in-plane anisotropy exists such that the in-plane g-factor can vanish under certain circumstances.