Generation of Broadband Frequency Entangled Biphotons for Quantum Clock Synchronization

  • Run-ai Quan
  • Rui-fang Dong
  • Fei-yan Hou
  • Yun Bai
  • Yu Zhang
  • Tao Liu
  • Shou-gang Zhang
Conference paper
Part of the Lecture Notes in Electrical Engineering book series (LNEE, volume 160)


Frequency entangled biphotons based on spontaneous parametric down conversion (SPDC) of nonlinear crystal are widely used in Quantum clock synchronization protocols. The time-correlation width of the entangled source determines the accuracy of the attainable synchronization, which relies on the spectral bandwidth of the generated biphotons. We theoretically investigate the generation of frequency anti-correlated biphotons from chirped periodically-poled potassium titanyl phosphate (C-PPKTP). It is demonstrated that an ultra-broadband entangled biphoton source with a width of 857 nm was obtained, by using a 10 mm-long crystal with a chirping of 9.7 × 10−6 μm−2, and a cw pumping source with a wavelength of 792 nm. The corresponding time correlation width is only 3.5 fs, which implies feasible clock synchronization accuracy in femtosecond scale. We further demonstrate that the narrowing of the time-correlation width slows down dramatically by increasing the chirping and the length of the nonlinear crystal, which provides a theoretical instruction for us to trade off between the complexity of the crystal fabrication and the sufficiently narrow time-correlation width.


Nonlinear Crystal Clock Synchronization Phase Match Condition Crystal Length Periodically Pole Lithium Niobate 
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The work has been supported by the National Natural Science Foundation of China (Grant No.11174282).


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Copyright information

© Springer-Verlag Berlin Heidelberg 2012

Authors and Affiliations

  • Run-ai Quan
    • 1
  • Rui-fang Dong
    • 1
  • Fei-yan Hou
    • 1
  • Yun Bai
    • 1
    • 2
  • Yu Zhang
    • 1
    • 2
  • Tao Liu
    • 1
  • Shou-gang Zhang
    • 1
  1. 1.Key Laboratory of Time and Frequency Primary Standards National Time Service Center, Chinese Academy of ScienceXianChina
  2. 2.Graduate University of Chinese Academy of ScienceBeijingChina

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