The Initial Experimental Guide to Implement QKD Polarization Encoding System at Telecom Wavelength

TL;DR

This paper demonstrates a laboratory-scale implementation of a polarization-encoded quantum key distribution system at telecom wavelength, achieving stable key exchange over a 5 km fiber with low error rate using simplified polarization basis.

Contribution

It presents the first experimental setup for polarization-encoded QKD at telecom wavelength with a single basis and continuous operation over 5 minutes.

Findings

Key rate of 10 bits/sec over 5 km fiber

Distributed 3000 bits with error rate less than 1%

Feasibility confirmed for simplified polarization basis QKD

Abstract

The experimental implementation of the polarization encoding system is presented using weak coherent pulses at a low enough frequency. The optical pulses are generated through intensity modulation at the repetition rate of $10$ pulses/sec with the intensity of $7\mu W$, whose polarization is modulated by the Pockel cell. For a $ 5$ km long fiber link, the key rate is thus limited to $ 10$ bits/sec accompanied by temporal synchronization among the Intensity Modulator (IM), Pockel cell, and the gate of the detector. The system was continuously operated for $5$ minutes, and $3000$ binary bits were distributed between two nodes with an error rate less than unity. We have used only a single polarization basis, i.e., horizontal and vertical polarizations, as the objective of this experiment is to validate the feasibility of the setup under simplified conditions, intended primarily for the laboratory-scale demonstrations.