8 research outputs found
Spin relaxation and antisymmetric exchange in n-doped III-V semiconductor
Recently K. Kavokin [Phys. Rev. B 64, 075305 (2001)] suggested that the
Dzyaloshinskii-Moriya interaction between localized electrons governs slow spin
relaxation in -doped GaAs in the regime close to the metal-insulator
transition. We derive the correct spin Hamiltonian and apply it to the
determination of spin dephasing time using the method of moments expansion. We
argue that the proposed mechanism is insufficient to explain the observed
values of the spin relaxation time.Comment: 5 pages, 1 figure
Spin-Orbit Coupling and Time-Reversal Symmetry in Quantum Gates
We study the effect of spin-orbit coupling on quantum gates produced by
pulsing the exchange interaction between two single electron quantum dots.
Spin-orbit coupling enters as a small spin precession when electrons tunnel
between dots. For adiabatic pulses the resulting gate is described by a unitary
operator acting on the four-dimensional Hilbert space of two qubits. If the
precession axis is fixed, time-symmetric pulsing constrains the set of possible
gates to those which, when combined with single qubit rotations, can be used in
a simple CNOT construction. Deviations from time-symmetric pulsing spoil this
construction. The effect of time asymmetry is studied by numerically
integrating the Schr\"odinger equation using parameters appropriate for GaAs
quantum dots. Deviations of the implemented gate from the desired form are
shown to be proportional to dimensionless measures of both spin-orbit coupling
and time asymmetry of the pulse.Comment: 10 pages, 3 figure