Generation Of Continuous Variable Quantum States From Optical Fiber For Quantum Information Splitting

Continuous variable quantum states have great application prospects in quantum information because they can be prepared deterministically and can be detected efficiently.Practical quantum information network need to be compatible with the existing fiber network and noiseless quantum information splitting to maintain the signal to noise ratio.In this thesis,we study the generation of continuous variable quantum light sources by using four wave mixing in optical fiber and the application in quantum information splitting.The content contains five parts and is listed as follows:(1)We theoretically study the quantum entanglement and temporal/spectrum property of the signal and idler fields of a pulse pumped fiber optical parametric amplifier.The study shows that the non-perfect mode matching will not only decrease the detection efficiency but also induce noise from other mode,and thus decrease the measured entanglement degree.Besides,the increasing of parametric gain will reduce the average mode number of signal/idler field.(2)We experimentally generate quadrature entanglement and multimode squeezed vacuum through non-degenerate four wave mixing and degenerate four wave mixing in dispersion shifted fiber pumped by mode-locked fiber laser,respectively.The measured inseparability of the entangled state is I=1.63(1.2 after correction for losses)which satisfy the criterion of inseparability I(27)2;the measured squeezing is 1.1±0.08dB(1.95±0.17dB after correction for losses).In the experiment,we analyze the limitation of the entangled degree and squeezing degree,which is helpful to improve the quantity of the generated continuous variable sources.(3)We experimentally realize low noise amplification and quantum signal splitting by coupling the generated entangled source into a pulse pumped fiber optical parametric amplifier.The measured noise figures of signal and idler ports are lower than a classical fiber optical parametric amplifier by 0.7±0.1dB and 0.84±0.09dB,respectively,which means low noise amplification is realized;The measured total transfer coefficient of the signal and idler ports of the quantum information splitter is?_s+?_i=1.5±0.2 which is larger than the classical limit 1,which means the quantum information tapping is realized.(4)By combining two linear splitters and a frequency degenerate but spatial non-degenerate parametric amplifier coupled with quantum correlation source,we theoretical design three way quantum information splitter.The theoretical analysis shows that the three-way quantum information splitter can split a quantum signal noiselessly with two of the outputs having signal amplified and the third almost at the input level and thus it is possible for cascade and scale-up.(5)We study the second-order correlation function of the individual signal and idler field generated through four wave mixing with a few coherent photons injected from theoretical and experimental aspects.We find that the output signal/idler field changes from Bose-Einstein distribution to Poisson distribution with the increasing of the injection of coherent photons,which can help to reduce the crosstalk between quantum channel and classical channel in the communication system.