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arXiv:quant-ph/0610185

Go and return propagation of biphotons in fiber and polarization entanglement

G. Brida, Maria V. Chekhova, Marco Genovese, Leonid A. Krivitsky, E. Predazzi

Published Oct 21, 2006• 0 citations
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Abstract

Propagation of entangled photons in optical fiber is one of the fundamental issues for realizing quantum communication protocols. When entanglement in polarization is considered, arises the problem of compensating for the fiber effect on photons polarization. In this paper we demonstrate an effective solution where a Faraday mirror allows to cancel undesired effects of polarization drift in fiber. This technique is applied to a protocol for generating Bell states by a narrow temporal selection of the second-order intensity correlation function.

DOI
10.48550/arxiv.quant-ph/0610185

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Propagation of entangled photons in optical fiber is one of the fundamental issues for realizing quantum communication protocols. When entanglement in polarization is considered, arises the problem of compensating for the fiber effect on photons polarization. In this paper we demonstrate an effective solution where a Faraday mirror allows to cancel undesired effects of polarization drift in fiber. This technique is applied to a protocol for generating Bell states by a narrow temporal selection of the second-order intensity correlation function.
Propagation of entangled photons in optical fibre is one of the fundamental issues for realizing quantum communication protocols. When entanglement in polarization is considered, a problem of compensating for the fibre effect on photons polarization arises. In this paper, we demonstrate an effective solution where a Faraday mirror allows us to cancel undesired effects of polarization drift in fibre. This technique is applied to a protocol for generating Bell states by a narrow temporal selection of the second-order intensity correlation function.
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Entanglement distribution through optical fibers is essential for quantum communication networks; however, fiber transmission can alter photon polarization and modify the observed correlations of polarization-entangled states, necessitating polarization compensation to recover the desired entangled state in the measurement basis. Here, we experimentally evaluate two passive polarization compensation techniques: a free-space Quarter-Half-Quarter (QHQ) waveplate configuration and an in-fiber three-paddle Fiber Polarization Controller (FPC). The polarization transformation along each downconverted-photon path is independently compensated through a systematic path-by-path optimization procedure. Using both techniques, we recover high-quality polarization correlations and entanglement, with visibilities exceeding 93%93\%93% in three mutually unbiased bases and fidelities above 94.5%94.5\%94.5%. The results demonstrate comparable restoration using free-space waveplate-based and fiber-based control, establishing a systematic framework for laboratory and short-reach quantum communication links.