| The security of traditional cryptography is based on computational complexity,while quantum key distribution utilizes the principle of quantum physics to guarantee the absolute security of communication.However,due to practical factors such as imperfect devices,there are some security vulnerabilities in the actual application of quantum key distribution.To address possible security vulnerabilities,we use the decoystate method to ensure the security of the source part,and the measurementdevice-independent quantum key distribution is used to overcome the loopholes of the detectors.Considering that practical measurement-deviceindependent quantum key distribution systems require auxiliary calibration systems for reference system sharing,the reference-frame-independent measurement-device-independent quantum key distribution protocol is proposed,which makes the reference system free from calibration and largely improves the practicality.In this paper,the relevant research on the improved four-intensity reference-frame-independent measurement-device-independent quantum key distribution protocol based on the double-scanning method is carried out,and specifics are shown below:1.The double-scanning method makes use of the technology of joint estimation and collective constraints to achieve tighter estimates of singlephoton yield and phase error rate,thereby effectively combating the statistical fluctuation caused by the finite key size effect.Therefore,we carried out the relevant theoretical study of the method based on the original four-intensity scheme,which included the construction of a security key rate model and the parameter estimation process.2.Reference-frame-independent measurement-device-independent quantum key distribution is immune to all the detector side-channel attacks and robust against unstable reference frames.However,the protocol introduces a large number of observations in the parameter estimation and its practical performance suffers a lot from the statistical fluctuation.In this work,we implement an improved four-intensity decoy-state method using the double-scanning on the original scheme.The simulation results show that the performance of the theoretical approach is significantly improved over the previous conventional three-intensity scheme.In addition,we propose the improved four-intensity reference-frame-independent measurement-device-independent quantum key distribution scheme with heralded single-photon sources.The scheme uses heralded single-photon sources containing a smaller vacuum state component instead of weak coherent sources while resisting the statistical fluctuation using the doublescanning method.The scheme was found to be effective in improving the key transmission distance,especially when the total number of pulses is not large.In addition,the scheme remains robust to reference system deviation under statistical fluctuation,and its performance increases with increasing reference system deviation angle. |
