The paper presents the first demonstration of spontaneous parametric down-conversion (SPDC) in a ferroelectric nematic liquid crystal (FNLC), enabling the tunable generation of entangled photon pairs. The efficiency of this process is comparable to that of the best nonlinear crystals. The emission rate and polarization state of the photon pairs can be significantly varied by applying a few volts or twisting the molecular orientation along the sample. This work introduces a new type of quasi-phased matching based on molecular twist structure, which allows for reconfiguration of the spectral and polarization properties of the generated photon pairs. The authors show that the two-photon polarization state can be altered via molecular orientation twist or an applied electric field, with the polarization state evolving from both photons polarized horizontally to vertically as the electric field is gradually applied. The study also investigates how the twist of molecular orientation along the sample affects the generated two-photon state, demonstrating that a broad range of two-photon polarization states can be achieved by engineering the source. The results highlight the potential of liquid crystals for practical applications in quantum technologies, offering superior performance and tunability compared to existing crystal SPDC or fiber sources.The paper presents the first demonstration of spontaneous parametric down-conversion (SPDC) in a ferroelectric nematic liquid crystal (FNLC), enabling the tunable generation of entangled photon pairs. The efficiency of this process is comparable to that of the best nonlinear crystals. The emission rate and polarization state of the photon pairs can be significantly varied by applying a few volts or twisting the molecular orientation along the sample. This work introduces a new type of quasi-phased matching based on molecular twist structure, which allows for reconfiguration of the spectral and polarization properties of the generated photon pairs. The authors show that the two-photon polarization state can be altered via molecular orientation twist or an applied electric field, with the polarization state evolving from both photons polarized horizontally to vertically as the electric field is gradually applied. The study also investigates how the twist of molecular orientation along the sample affects the generated two-photon state, demonstrating that a broad range of two-photon polarization states can be achieved by engineering the source. The results highlight the potential of liquid crystals for practical applications in quantum technologies, offering superior performance and tunability compared to existing crystal SPDC or fiber sources.