Study On Polarization-entangled Quantum Source Based On Four-wave Mixing In Fiber

Entangled photons are important and basic resource for studying quantum information,which are prominently applied in quantum key distribution,quantum teleportation,quantum dense coding,quantum metrology and so on.The fabrication of quantum source which can generate entangled photon pairs is concerned by academia as a result of wide application of entangled photons,how to obtain a quantum source with flexible structure,small size,low cost and practicality is also brought into focus.In this paper,the theory of spontaneous four-wave mixing process in fiber is explained in detail,and the parametric gain expression and phase matching conditions are obtained.On this basis,a portable polarization-entangled quantum source was fabricated based on the spontaneous four-wave mixing in dispersion-shifted fiber.The main work includes:1.The device of polarization-entangled quantum source based on the spontaneous four-wave mixing process in optical fiber was fabricated,and the polarization-entangled signal and idler photon pairs were generated with wavelengths of 1558.17 nm and 1548.51 nm respectively by pumping 500 m dispersion-shifted fiber with pump pulse,the wavelength of pump is 1553.33 nm.2.The design and debugging of the electronic system of the quantum source were completed.The electronic system can realize photoelectric conversion of the optical signal,and simultaneously complete programmable delay and frequency division of electrical signal.The output TTL electrical signal of electronic system can be used as synchronous clock trigger for single photon detector and data acquisition.3.The performance of the electronic system was tested,single-channel photon counting experiment and the coincidence counting experiment of entangled photon pairs were carried out as well.The experimental results show that electronic system of quantum source can achieve the specified frequency division and delay,the average absolute error of the frequency division measurement result is 0.013 MHz,and the maximum error of the delay measurement results is 0.096 ns compared with the fitting results.The ratio between coincidence and accidental coincidence rates is 22.8 when the mean photon number in the signal and idler channel is 0.0007 pairs/pulse,and visibility of polarization-entangled interference fringe is 0.87.