Measuring the time–frequency properties of photon pairs: A short review

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.

Quantum-Enhanced Doppler Radar/Lidar

“…Thus, the POVMs {|ω, ω ω, ω|} are actually phase insensitive. Finally, we prove that Fq = J q , so this measurement also saturates the QFI in Section V. Let us remark that this measurement does not depend on the parameter λ, so it can be used for saturating the QFI for any velocity, and that it could in principle be experimentally feasible [49,50]. Finally, notice that, by using phases-sensitive measurements, the precision could be further enhanced, but this may require further information about the target, such as its location.…”

Measuring higher-order photon correlations of faint quantum light: a short review

“…( 21), is demonstrated, which incorporates a strong anti-correlation in the frequency space. The exact shape of the joint spectral correlations of signal and idler ordinarily stems from the dispersion properties of the used material [147][148][149]. Such strong spectral correlations result in multimodal PDC emission.…”

Photonic Quantum Metrology

“…Other methods different from QP and SLM can be exploited to manipulate and measure OAM states, as shown in Refs. 363-369. Time-bin [370][371][372] and time-frequency [373][374][375][376] degrees of freedom can be also exploited as quantum resources. For such encodings, photon manipulation can be done through interferometric schemes 169 .…”