Fast Quantifier of High‐Dimensional Frequency Entanglement through Hong–Ou–Mandel Interference

Abstract

High-dimensional frequency entanglement is an enabling resource in quantum technology due to its high information capacity and error resilience.A concise yet efficient method for precisely quantifying its dimensionality remains an open challenge, owing to the difficulties for performing required superposition measurements in energy-time domains, and the complexity associated with full quantum state tomography that scales unfavorably with dimensions. With the assistance of Hong-Ou-Mandel experiment that performs a Fourier transform between the entangled photons in terms of joint spectral intensities and the quantum interference in terms of biphoton temporal coincidences, the concept of Shannon dimensionality as a fast quantifier of bipartite continuous frequency entanglement is unlocked. This quantitative technique reveals the complete distribution of frequency entanglement but without suffering from any limitation of modal capacity of the detection geometry. These results may significantly facilitate the use of quantum interference for characterizing the high-dimensional entanglement nature by avoiding some stringent conditions.

Controllable transitions among phase-matching conditions in a single nonlinear crystal

“…One remarkable finding of this study is the observation of three phase-matching conditions matched within a very short pump wavelength range of 401-408 nm. This wavelength range, particularly around 405 nm, holds significant importance for entangled photon sources, being widely utilized not only in the laboratory [33][34][35] but also in satellite-based endeavors [36] . The popularity of this wavelength range can be attributed to the maturity of blue-violet laser technology, which allows the production of high-power blue lasers at relatively affordable costs [37][38][39][40][41][42] .…”