High-fidelity transmission of quantum polarization states through birefringent optical fibers
Takeshi Ozeki · Physical Review A · 2006
High fidelity transmission of quantum polarization states is essential for realizing quantum networks. The degenerate ${\ensuremath{\Psi}}^{\ensuremath{-}}$ state is an eigenstate of a transmission fiber. In this paper we propose a method for preparing the degenerate ${\ensuremath{\Psi}}^{\ensuremath{-}}$ state using spontaneous four wave mixing (SFWM) in a fiber Sagnac loop excited by two orthogonally polarized pump waves. This configuration includes a 45\ifmmode^\circ\else\textdegree\fi{} Faraday rotator, which creates a relative phase of $\ensuremath{\pi}$ between the two counterpropagating entangled photon pairs with indistinguishability both in frequencies and generation paths. We confirm that only the amplitude is degraded in the output wave form of nonlinear sum frequency generation in the Bell state analyzer after propagation through the fiber due to the polarization mode dispersion.