Efficiencies of Quantum Optical Detectors

TL;DR

This paper introduces a universal definition of quantum optical detector efficiency based on maximum permissible optical loss, and proves that linear optical processing cannot enhance detector efficiency.

Contribution

It provides a universal efficiency definition applicable to all quantum optical detectors and demonstrates the impossibility of increasing efficiency through linear optical processing.

Findings

Universal efficiency definition for quantum detectors

Linear optical processing cannot increase detector efficiency

Efficiency is limited by maximum optical loss

Abstract

We propose a definition for the efficiency that can be universally applied to all classes of quantum optical detectors. This definition is based on the maximum amount of optical loss that a physically plausible device can experience while still replicating the properties of a given detector. We prove that detector efficiency cannot be increased using linear optical processing. That is, given a set of detectors, as well as arbitrary linear optical elements and ancillary light sources, it is impossible to construct detection devices that would exhibit higher efficiencies than the initial set.