Weak measurement of quantum dot spin qubits

TL;DR

This paper develops a theoretical framework for weak measurements of quantum dot spin qubits, integrating experimental techniques and environmental effects to enable quantum state control, tomography, and undemolition.

Contribution

It introduces a comprehensive control cycle for quantum dot spin qubits incorporating weak measurement, state tomography, and quantum undemolition, grounded in realistic experimental conditions.

Findings

Identifies a regime where nuclear spin environment simplifies weak measurement dynamics

Proposes a control cycle combining ESR, spin blockade, and Coulomb blockade techniques

Discusses methods for quantum state undemolition and dephasing mitigation

Abstract

The theory of weak quantum measurements is developed for quantum dot spin qubits. Building on recent experiments, we propose a control cycle to prepare, manipulate, weakly measure, and perform quantum state tomography. This is accomplished using a combination of the physics of electron spin resonance, spin blockade, and Coulomb blockade, resulting in a charge transport process. We investigate the influence of the surrounding nuclear spin environment, and find a regime where this environment significantly simplifies the dynamics of the weak measurement process, making this theoretical proposal realistic with existing experimental technology. We further consider spin-echo refocusing to combat dephasing, as well as discuss a realization of "quantum undemolition", whereby the effects of quantum state disturbance are undone.