  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.
