Readout of a single electron spin in a double quantum dot using a quantum point contact

TL;DR

This paper models the dynamics of a single electron spin in a double quantum dot and demonstrates how a quantum point contact can be used for effective spin readout, considering hyperfine interactions and electron injection verification.

Contribution

It provides a microscopic model and rate equations for spin readout in double quantum dots, including analysis of one and two-electron cases with hyperfine interactions.

Findings

Distinct current signatures for different spin states in one-electron case

Effective spin readout in two-electron case considering hyperfine interactions

Method to verify electron injection success via QPC current variations

Abstract

We study the dynamics of a single electron spin in a double quantum dot (DQD) and its readout via a quantum point contact (QPC). We model the system microscopically and derive rate equations for the reduced electron density matrix of the DQD. Two cases with one and two electrons in the DQD are studied. In the one-electron case, with different Zeeman splittings in the two dots, the electron spin states are distinctly characterized by a constant and an oscillatory current through the QPC. In the two-electron case, the readout of the spin state of the electron in one of the dots called the qubit dot is essentially similar after considering hyperfine interactions between the electrons and the nuclear spins of the host materials and a uniform magnetic field applied to the DQD. Moreover, to ensure that an electron is properly injected into the qubit dot, we propose to determine the success of the electron injection from the variations of the QPC current after applying an oscillating magnetic field to the qubit dot.