Polarization-independent phase-coded quantum key distribution system and method

Abstract

The invention discloses a polarization-independent phase encoding quantum key distribution system and method. A sending end comprises a pulse laser, an intensity modulator, an optical fiber isolator,a phase encoding unit and an electrically adjustable attenuator which are connected in sequence. A receiving end comprises an optical fiber circulator, a phase decoding unit, a first single photon detector and a second single photon detector. The phase decoding unit is composed of an unequal-arm Mch (Zehnder) interferometer and a Sagnac ring. Compared with the prior art, polarization changes of along arm and a short arm of an MZ interferometer can be automatically compensated, and polarization consistency of two paths of pulses passing through the long arm and the short arm is ensured so thatchannel polarization disturbance resistance is realized. The requirement on the voltage amplitude of the phase modulator is low. Due to the introduction of the Sagnac ring, two polarization components of one optical pulse respectively pass through the phase modulator from opposite directions, equivalently, the whole optical pulse is only subjected to phase modulation once, so that insertion lossis small, working rate of the system is not limited by the structure and can reach more than GHz, and key productivity is greatly improved.

Description

technical field [0001] The invention relates to the technical field of quantum polarization encoding, in particular to a polarization-independent phase encoding quantum key distribution system and method. Background technique [0002] The optical fiber quantum key distribution system generally uses single-mode optical fiber as the transmission channel, but due to the inherent birefringence effect of the optical fiber channel, the polarization state of the photon will change during the transmission process, and will change with the change of the external environment, so that The polarization state of photons as they enter the receiving end is unpredictable. Therefore, the traditional quantum key distribution system based on the double unequal arm Mach-Zehnder interference ring scheme has poor stability and is susceptible to environmental interference. [0003] In order to improve the stability and practicability of the quantum key distribution system, researchers have propos...

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Problems solved by technology

But this solution will double the loss and reduce the efficiency of the system by half

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