Multi-user orbital angular momentum multiplexing network system and quantum key distribution method thereof

Abstract

The invention discloses a multi-user orbital angular momentum multiplexing network system, comprising an Alice control terminal, an S-D type orbital angular momentum multiplexing unit and a Bob user terminal, wherein the Alice control terminal comprises a laser source, a polarization controller, an attenuator, a first non-equal arm M-Z interferometer and an orbital angular momentum multiplexing unit; the orbital angular momentum demultiplexing unit comprises a Dammam grating, a second collimator and a single-mode fiber; the Bob user terminal comprises N Bob users; the laser source generates a light signal, the light signal is transmitted to the first non-equal arm M-Z interferometer after entering the polarization controller and the attenuator and is sequentially transmitted to the orbital angular momentum multiplexing unit and the orbital angular momentum demultiplexing unit; and finally, the light signal enters the Bob users for detection. The multi-user orbital angular momentum multiplexing network system disclosed by the invention is used for achieving one-to-many communication of quantum network communication of a free space, individual users are relatively independent, and the user number can be expanded with the increase of the orbital angular momentum multiplexing, so that the expandability is good.

Description

technical field [0001] The invention relates to the field of free space communication and quantum communication network, in particular to a multi-user orbital angular momentum multiplexing network system and a quantum key distribution method thereof. Background technique [0002] Quantum cryptography is based on Heisenberg's uncertainty principle and the principle that unknown quantum states cannot be cloned. Its security does not depend on the complexity of calculation, so it has absolute security. Quantum Key Distribution (QKD) can allow legitimate participants in different geographical locations to share keys in an absolutely secure manner. The key transmission channel of both parties can be free space or optical fiber. QKD using optical fiber as the transmission channel has achieved Great progress. [0003] At present, a scheme using M-Z interferometers to realize quantum key distribution, whose interference events clearly reflect the path selection problem in quantum m...

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Problems solved by technology

The measurement capability of ordinary forked amplitude gratings is limited due to the low diffraction efficiency of its high-order diffraction orders

The energy ratio of the zero-order, first-orde

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