Concepedia

Single-photon quantum-nondemolition detectors constructed with linear optics and projective measurements

Pieter Kok, Hwang Lee, Jonathan P. Dowling

Physical Review A · 2002 · 174 citations · 32 references

Open access

TL;DR

Optical quantum‑nondemolition devices can provide essential tools for quantum information processing. The study describes optical interferometers that detect a single photon without destroying it. The authors present entanglement‑assisted and non‑entanglement‑assisted interferometers, including ideal and realistic detectors, and expanded protocols that preserve photon polarization. Detectors with 88 % quantum efficiency and single‑photon resolution can achieve output fidelities up to 89 %, while polarization‑preserving protocols can reach up to 98.5 %.

Abstract

Optical quantum-nondemolition devices can provide essential tools for quantum information processing. Here, we describe several optical interferometers that signal the presence of a single photon in a particular input state without destroying it. We discuss both entanglement-assisted and nonentanglement-assisted interferometers, with ideal and realistic detectors. We found that the existing detectors with 88% quantum efficiency and single-photon resolution can yield output fidelities of up to 89%, depending on the input state. Furthermore, we construct expanded protocols to perform quantum-nondemolition detections of single photons that leave the polarization invariant. For detectors with 88% efficiency, we found polarization-preserving output fidelities of up to 98.5%.