# One-Time Shot-Noise Unit Calibration Method for Continuous-Variable Quantum Key Distribution

## TL;DR

This paper introduces a one-step calibration method for the shot-noise unit in continuous-variable quantum key distribution, enhancing security, simplifying the process, and enabling real-time automatic operation.

## Contribution

A novel one-time calibration model based on a trusted detector approach that closes practical loopholes and simplifies shot-noise unit evaluation in CV-QKD systems.

## Key findings

- Effective one-step calibration reduces statistical fluctuations.
- Security analysis confirms robustness against collective attacks.
- Experimental results validate practical applicability.

## Abstract

The shot-noise unit in continuous-variable quantum key distribution plays an important and fundamental role in experimental implementation as it is used as a normalization parameter that contribute to perform security analysis and distill the key information. However, the traditional calibration procedure and detector model can not cover all system noise in practical application, which will result in some loopholes and influence the practical security. What's more, the traditional procedure is also rather complicated and has difficulty in compatible with automatic operating system. In this paper we propose a calibration model based on the proposed trusted detector model, which could naturally close the loopholes in practical application. It can help identify the shot-noise unit in only one step, which can not only effectively simplify the evaluation process but also reduce the statistical fluctuation, while two steps are needed in traditional method. We prove its feasibility and derive the complete version of the corresponding entanglement-based model. Detailed security analysis against arbitrary collective attacks and numerous simulation results in both the asymptotic limit regime and the finite-size regime are provided. A proof-of-principle experiment has been implemented and the results indicate that the one-time-calibration model can be employed as a powerful substitution to calibrate the shot-noise unit. Our method paves the way for the deployment of continuous-variable quantum key distribution with real time calibration and automatic operation.