Quantum Gates with Spin States in Continuous Microwave Field

The physical basis of the method of implementing quantum logical operations in a continuous microwave field in a system of two electrons with different g-factors and a constant exchange interaction is developed. A small variable additive ΔB(t) to the magnetic field is proposed as a control action. It is obtained that a simple functional dependence ΔB(t), based on harmonic functions, allows us to perform elementary quantum logical operations and their sequences. This method is adapted to the experimental conditions.     

On the process of hole trapping in Ge/Si heterostructures with Ge quantum dots

Admittance spectroscopy is used to determine the cross sections and energy levels of holes in Ge/Si heterostructures with Ge quantum dots. The structures are grown by molecular-beam epitaxy. It is established that, in layers of quantum dots produced at low growth temperatures T _g ≤ 450°C, the capture cross section for hole trapping into quantum dots exponentially increases with increasing hole binding energy (the Meyer-Neldel rule), with the same characteristic energy ～25 eV independent of T _g . It is shown that the Meyer-Neldel rule is violated in structures grown at higher temperatures or in samples treated in hydrogen plasma. In the case of nanoclusters synthesized at low temperatures, the experimental results suggest that charge-carrier trapping into Ge quantum dots proceeds via the electron-phonon mechanism with the participation of structural defects.