Theoretical study on quantum dynamics in single-electron quantum-dot pump

Abstract

A quantum-dot pump is an on-demand single-electron source which has the unique property of emitting hot electrons of $\sim$100 meV above Fermi energy with very small pumping error of order 0.1 part per million. In order to utilize it for a quantum metrology as well as a fermion version of optics and related quantum processing, it is important to understand the quantum dynamics during the pumping. Due to the unique property of the quantum-dot pump, the dynamics involves complications such as a non-equilibrium electron-capturing process, which determines the pumping accuracy, nonadiabatic electron-wave-packet evolution in the pump and its tunneling through a quantum-dot barrier, which determines the wave-function characteristics, and relaxation of hot electron emitted from the pump, which affects the coherence of the pumped electron.

In this thesis, we present a series of our studies concerning aforementioned complications. First, we analyze how the potential shape of the quantum-dot affects the capturing process and the pumping accuracy. We find that the improvement of the pump accuracy observed in a anisotropic quantum-dot potential was mainly due to the thicker potential barrier. Second, we study the relaxation mechanism of the pumped electron by scattering with phonons. We calculate the scattering rate between hot electron and phonons and elucidated the mechanism of the suppression of the scattering which was observed in the pump under a strong magnetic field. Lastly, we propose how to generate and detect an electron in a Gaussian state, using a quantum-dot pump with gigahertz operation and realistic parameters. The proposal is based on our finding on general properties (coherent-state motion and tunneling dynamics) of electron wave packet in a 2D dynamic quantum dot under a strong magnetic field.