Manipulation of double-dot spin qubit by continuous noisy measurement

TL;DR

This paper investigates how continuous weak charge measurement affects the spin dynamics of a double quantum dot two-electron qubit, revealing measurement-induced effects like quantum Zeno stabilization and state transitions.

Contribution

It provides analytical and numerical analysis of measurement-induced spin dynamics in a double quantum dot system under various coupling regimes, highlighting novel effects.

Findings

Negative-result evolution observed

Quantum Zeno effect induces system stabilization

Unitary singlet-triplet evolution caused by measurement

Abstract

We consider evolution of a double quantum dot (DQD) two-electron spin qubit which is continuously weakly measured with a linear charge detector (quantum point contact). Since the interaction between the spins of two electrons depends on their charge state, the charge measurement affects the state of two spins, and induces non-trivial spin dynamics. We consider the regimes of strong and weak coupling to the detector, and investigate the measurement-induced spin dynamics both analytically and numerically. We observe emergence of the negative-result evolution and the system stabilization due to an analog of quantum Zeno effect. Moreover, unitary evolution between the triplet and a singlet state is induced by the negative-result measurement. We demonstrate that these effects exist for both strong and weak coupling between the detector and the DQD system.