High-extinction ratio optical pulse generation method suitable for CVQKD system

Abstract

The invention discloses a high-extinction ratio optical pulse generation method suitable for a CVQKD system. Continuous light generated by a laser enters a BS through a CIR, and then is divided into two beams BS3 and BS4 according to an intensity splitting ratio; an optical signal output from BS3 is rotated and transmitted clockwise through a loop, then returns to a polarization-maintaining optical coupler BS through BS4, and then is divided into two beams S341 and S342; the optical signal output from BS4 is rotated and transmitted counterclockwise through the loop, then returns to the polarization-maintaining optical coupler BS through BS3, and then is divided into two beams S431 and S432, wherein the interference results of S341 and S431 are output from CIR3 to the Port 2, and the interference results of S342 and S432 are output from BS2 to the Port3. Compared with the prior art, the scheme of the invention has the positive effects of low cost, simple and reliable implementation, frequency multiplication and extremely high extinction ratio.

Description

technical field [0001] The invention relates to a method for generating high extinction ratio light pulses suitable for continuous variable quantum cryptography systems. Background technique [0002] In continuous variable quantum key distribution systems, the generation of high extinction ratio optical pulses is a key technology in the preparation of quantum state signals, which affects the security code rate of the system. The light intensity of the signal at the sending end of the key distribution system is very weak, usually on the order of tens of photons / pulse. However, due to the use of balanced homodyne detection at the receiving end of the system, the intensity of the local oscillator light is required to be very high, usually at 10 8 / pulse magnitude. Therefore, how to obtain an optical pulse with a high extinction ratio, so that the residual photons in the "light-free part" of the split local oscillator optical pulse are as small as possible, so as to reduce its...

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Problems solved by technology

The method of using cascaded intensity modulators to realize high extinction ratio light pulses has a complex system composition, requires many external feedback monitoring signals, and the system stability is not good; in addition, a single-stage intensity modulator with a particularly high extinction ratio index is used, which is currently on the market. It is difficult to find commercial devices with this performance on the Internet, and individual customization is limited by factors such as physical processes, making it difficult and costly to realize

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