2025/04/27 by D. Scharwald, Scharwald, D., Polina R. Sharapova +2 · 1 citation
Engineering · Physics and Astronomy · #Advanced Fiber Laser Technologies #Advanced Frequency and Time Standards #FOS: Physical sciences #Optical Network Technologies #Quantum Physics (quant-ph) #quant-ph
paper · pdf · doi:10.48550/arxiv.2504.19377
published as Phys. Rev. Research 8, 033139 (2026)
openalex publication_date 2025/04/27 · openalex created_date 2025/10/10 · arxiv created 2026/05/30 · openalex updated_date 2026/08/01 · arxiv updated 2026/08/05
Multimode quantum light has promising applications in many areas of physics, such as quantum communications and quantum computing. However, its multimode nature also makes it challenging to measure its properties. Recently [Optica Quantum 3, 36 (2025)], a technique for the simultaneous measurement of squeezing of multiple broadband modes based on a phase-sensitive amplification approach was experimentally implemented using a setup that effectively corresponds to an SU(1,1) interferometer. Here, we aim to provide a complete theoretical analysis of the modal structure of SU(1,1) interferometers (generally unbalanced) and a detailed theoretical formal derivation of the framework for this technique. Utilizing the joint Schmidt decomposition of the transfer functions, we investigate the shape and phase profiles of the modes of the SU(1,1) interferometer and its components [parametric down-conversion (PDC) sections] for different parametric gain regimes. We discover a complicated interplay between the PDC modes and the modes of the entire interferometer, and analyze it by using their overlap coefficients as a similarity measure. Finally, we develop a rigorous processing method for the aforementioned multimode squeezing measurement technique and discuss necessary approximations to make this method experimentally feasible.