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Bulletin of the Russian Academy of Sciences Physics

Analysis of Schmidt Modes of Ultra-Broadband Biphotons Generated in a Photonic Crystal Fiber

Maksim A. Smirnov, A. M. Smirnova, A. F. Khairullin, O. A. Ermishev, Sergey A. Moiseev

Published Dec 1, 2024• 4 citations
Publisher

Abstract

We presented numerical estimates of the degree of quantum entanglement based on Schmidt mode analysis for ultra-broadband biphotonic states generated in a photonic crystal fiber. We show that these states have a high degree of quantum entanglement even when the source is pumped broadband by femtosecond laser pulses.
DOI
10.1134/s1062873824708535

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We present a time-domain Schmidt-mode analysis of a broadband continuous-variable entanglement of photon pairs generated via a vectorial four-wave mixing (FWM) of ultrashort laser pulses in a highly nonlinear birefringent optical fiber. We demonstrate that the time-domain eigenmodes of high-purity two-photon states generated through vectorial FWM can be steered, by varying the pump wavelength and FWM polarization geometry, from a high-purity entangled ket to a high-entropy entangled state in a space of a very high dimensionality. Moreover, this pulse-mode analysis is shown to provide a clear physical perspective on how the entanglement structure of two-photon states builds up as a result of short-pulse FWM dynamics. This insight reveals a correspondence-type relation between the quantum and classical pictures of photon-pair generation. With an eye on practical applications, a clear understanding of the temporal profile of pulse modes representing high-purity two-photon states is central to a meaningful shaping of ultrashort photon-packet waveforms for super-resolving microscopy and multiphoton spectroscopy using quantum states of light.