BEGIN:VCALENDAR VERSION:2.0 PRODID:researchseminars.org CALSCALE:GREGORIAN X-WR-CALNAME:researchseminars.org BEGIN:VEVENT SUMMARY:P.R. Sharapova DTSTART:20240910T092000Z DTEND:20240910T102000Z DTSTAMP:20260423T040215Z UID:QOART/47 DESCRIPTION:Title: M ultimode squeezing: generation and characterization\nby P.R. Sharapova as part of Quantum Optics and Related Topics\n\n\nAbstract\nMultimode squ eezed light is an increasingly popular tool in photonic quantum technologi es\, including sensing\, imaging\, and computing [1]. In metrology\, it pr ovides the measurement of the phase beyond the classical sensitivity limit [2\,3]\, its role was crucial for the first observation of gravitational waves [4]. At the same time\, multiple squeezed modes are promising tools for continuous-variable quantum computing\, quantum information processing and quantum communication\, where each mode (qumode) serves as an informa tion carrier and a large set of modes can be used for the cluster sates ge neration and measurement-based quantum computation [5].\nWith numerous app lications of multimode squeezed light\, it is important to characterize sq ueezing in multiple spatial and temporal modes taking into account interna l losses in the system: \nWhen PDC is generated in transparent bulk nonlin ear crystals the absorption is small enough to be neglected\, however\, in ternal losses can be significant for structured media like waveguides\, wh ere the guided light can be lost due to scattering from surface roughness. \nWe investigate the mode structure of lossy broadband multimode squeezed light and show how the maximal possible squeezing can be extracted and mea sured. In opposite to an ideal multimode squeezed states\, where the uniqu e basis of Schmidt modes can be found via Bloch-Messiah reduction of Bogol iubov transformation [6]\, the broadband basis of Schmidt modes for lossy squeezed states cannot be uniquely defined. We introduce a new type of bro adband basis for lossy systems in which the squeezing is maximized\, i.e.\ , the upper bound for squeezing is reached\, and show how these modes can be constructed [7].\nFurthermore\, the existing experimental methods of mu ltimode squeezed vacuum characterization (homodyne detection\, projective filtering) are technically complicated\, and in the best case\,\ndeal with a single mode at a time. We present a method [8] based on a cascaded syst em of nonlinear crystals to simultaneously measure squeezing in different spatial modes. In such a system\, the second crystal serves as an amplifie r/deamplifier for the squeezed light generated in the first crystal (squee zer). The direct intensity measurement of light after the amplifier allows us to reconstruct the squeezing of the light generated in the first cryst al.\n\n[1] U. L. Andersen\, T. Gehring\, C. Marquardt\, and G. Leuchs\, Ph ys. Scr. 91 053001 (2016).\n\n[2] V. Giovannetti\, S. Lloyd\, and L. Macco ne\, Science 306\, 1330-1336 (2004).\n\n[3] D. Scharwald\, T. Meier\, P. R . Sharapova\, Phys. Rev. Research 5\, 043158 (2023).\n\n[4] B.P. Abbott et al. (LIGO Scientific Collab. and Virgo Collab.)\, Phys. Rev. Lett. 119\, 161101 (2017).\n\n[5] M. V. Larsen\, X. Guo\, C. R. Breum\, J. S. Neergaar d-Nielsen\, U. L. Andersen\, Science 366\, 6463 (2018).\n\n[6] M. G. Rayme r and I. A. Walmsley\, Phys. Scripta 95\, 064002 (2020).\n\n[7] D. A. Kopy lov\, T. Meier\, P. R. Sharapova\, arXiv:2403.05259 (2024).\n\n[8] I. Bara kat\, M. Kalash\, D. Scharwald\, P. R. Sharapova\, N. Lindlein\, M. V. Che khova\, arXiv:2402.15786 (2024).\n LOCATION:https://researchseminars.org/talk/QOART/47/ END:VEVENT END:VCALENDAR