Measuring the time-frequency properties of photon pairs: a short review

TL;DR

This review discusses the importance of characterizing the time-frequency properties of photon pairs for quantum information applications, highlighting methods for measuring and retrieving their spectral wavefunctions.

Contribution

It provides a comprehensive overview of theoretical and technical methods for characterizing two-photon time-frequency states, including adaptations of classical metrology.

Findings

Detailed methodologies for measuring frequency correlations

Techniques for retrieving the full spectral wavefunction

Integration of classical metrology schemes at the single-photon level

Abstract

Encoding information in the time-frequency domain is demonstrating its potential for quantum information processing. It offers a novel scheme for communications with large alphabets, computing with large quantum systems, and new approaches to metrology. It is then crucial to secure full control on the generation of time-frequency quantum states and their properties. Here, we present an overview of the theoretical background and the technical aspects related to the characterization of time-frequency properties of two-photon states. We provide a detailed account of the methodologies which have been implemented for measuring frequency correlations and for the retrieval of the full spectral wavefunction. This effort has benefited enormously from the adaptation of classical metrology schemes to the needs of operating at the single-photon level.