Four-state quantum encoder and decoder for phase modulation polarization encoding and quantum key distribution system

Abstract

The invention discloses a four-state quantum encoder and decoder for phase modulation polarization encoding and a quantum key distribution system. The encoder and the decoder have intrinsic stability, namely, the working stability is not influenced by the external environment or connecting optical fibers which can be common mono-mode optical fibers. The quantum encoder and decoder can be applied to the field of quantum key distribution, the whole system comprises a transmitting end and a receiving end, and the transmitting end and the receiving end are connected through a quantum channel to complete the key distribution process. The quantum encoder and decoder can achieve BB84 protocol four-state quantum key encoding and decoding with intrinsic stability. The common mono-mode optical fibers can be used as all the connecting optical fibers without using polarization-maintaining optical fibers, and interference with the phase drift and polarization change of the system from the external environment has no influence on the encoding or decoding process at all.

Description

technical field [0001] The invention relates to the field of quantum communication, in particular to an inherently stable phase modulation polarization coding four-state quantum encoder and decoder and a quantum key distribution system. Background technique [0002] In quantum secure communication technology, the most commonly used encoding methods are phase encoding and polarization encoding. In the past, polarization encoding usually uses two linear polarization states of photons to encode, that is, electro-optic crystals or Pockels cells are used to encode the linear polarization states of photons, but the half-wave voltage of electro-optic crystals or Pockels cells is very high (several thousand volts). , it is very inconvenient to use, and it is difficult to achieve high-speed encoding. However, if two mutually perpendicular linearly polarized lights are used to synthesize, the final polarized light is determined by the phase difference between the two mutually perpend...

AI Technical Summary

Problems solved by technology

The stability of the output polarization state is affected by two factors. One is that there is a phase shift in the transmission optical path of the two polarization components from beam splitting to combining, so that the output polarization state cannot completely depend on the phase of the system modulation. It is also affected by two Due to the influence of the phase drift of the transmission optical path, it is impossible to output a stable polarization state; the second is the problem of maintaining the polarization state of the two polarization components in the process of beam splitting and combining. At present, there is no intrinsically stable polarization state maintaining structure. Polarization-maintaining fiber is used in each transmission optical path, and cheap and easy-to-process single-mode fiber cannot be used. The principle of using polarization-maintaining fiber at the same time is to introduce a special transmission medium with high birefringence, and it is still impossible to maintain the two perfectly in theory. Polarization state of the polarized component

[0004] Among the encoders and decoders for phase modulation and polarization encoding that have been published so far, there are mainly phase modulation polarization encoding structures based on M-Z interferometer and Sagnac ring interferometer, but none of them can simultaneously realize the intrinsic Stable Phase Modulation Polarization Encoding

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