Quantum measurement of a solid-state qubit: A unified quantum master equation approach revisited

TL;DR

This paper revisits the quantum measurement of solid-state qubits using a unified quantum master equation approach, analyzing relaxation and dephasing effects during measurement at various voltages and temperatures.

Contribution

It introduces a comprehensive quantum master equation framework that accounts for energy exchange, enabling analysis of measurement-induced decoherence in solid-state qubits under diverse conditions.

Findings

Detailed-balance relation derived and emphasized

Numerical and analytical results for relaxation and dephasing presented

New features identified relevant to future experiments

Abstract

Quantum measurement of a solid-state qubit by a mesoscopic detector is of fundamental interest in quantum physics and an essential issue in quantum computing. In this work, by employing a unified quantum master equation approach constructed in our recent publications, we study the measurement-induced relaxation and dephasing of the coupled-quantum-dot states measured by a quantum-point-contact. Our treatment pays particular attention on the detailed-balance relation, which is a consequence of properly accounting for the energy exchange between the qubit and detector during the measurement process. As a result, our theory is applicable to measurement at arbitrary voltage and temperature. Both numerical and analytical results for the qubit relaxation and dephasing are carried out, and new features are highlighted in concern with their possible relevance to future experiments.