Quantum-Limited Measurement and Information in Mesoscopic Detectors

TL;DR

This paper establishes the fundamental conditions for mesoscopic detectors to achieve quantum-limited measurement efficiency, applicable to both interacting and non-interacting systems, and analyzes the symmetries needed in scattering matrices.

Contribution

It derives general conditions for quantum-limited measurement in mesoscopic detectors and examines symmetry requirements in scattering matrices to reach this limit.

Findings

Conditions for quantum-limited measurement are identified.

Symmetries in scattering matrices are necessary for optimal efficiency.

Non-interacting scattering detectors can reach the quantum limit under specific conditions.

Abstract

We formulate general conditions necessary for a linear-response detector to reach the quantum limit of measurement efficiency, where the measurement-induced dephasing rate takes on its minimum possible value. These conditions are applicable to both non-interacting and interacting systems. We assess the status of these requirements in an arbitrary non-interacting scattering based detector, identifying the symmetries of the scattering matrix needed to reach the quantum limit. We show that these conditions are necessary to prevent the existence of information in the detector which is not extracted in the measurement process.