Performance analysis of quantum key distribution using polarized coherent-states in free-space channel

In free space channel,continuous-variable quantum key distribution(CV-QKD)using polarized coherent-states can not only make the signal state more stable and less susceptible to interference based on the polarization non-sensitive of the free-space channel,but also reduce the noise introduced by phase interference.However,arbitrary continuous modulation can not be carried out in the past polarization coding,resulting in that the signal state can not obtain arbitrary continuous value in Poincare space,and the security analysis of CV-QKD using polarized coherent-states in free space is not complete.Here we propose a new modulation method to extend the modulation range of signal states with an optical-fiber-based polarization controller.In particular,in terms of the main influence factors in the free-space channel,we utilize the beam extinction and elliptical model when considering the transmittance and adopt the formulation of secret key rate.In addition,the performance of the proposed scheme under foggy weather is also taken into consideration to reveal the influence of severe weather.Numerical simulation shows that the proposed scheme is seriously affected by attenuation under foggy weather.The protocol fails when visibility is less than 1 km.At the same time,the wavelength can affect the performance of the proposed scheme.Specifically,under foggy weather,the longer the wavelength,the smaller the attenuation coefficient,and the better the transmission performance.Our proposed scheme can expand the modulation range of signal state,and supplement the security research of the scheme in the free-space channel,thus can provide theoretical support for subsequent experiments.

Continuous-Variable Measurement-Device-Independent Quantum Key Distribution with One-Time Shot-Noise Unit Calibration

Imperfections in practical detectors,including limited detection efficiency,and inherent electronic noise,can seriously decrease the transmission distance of continuous-variable measurement-device-independent quantum key distribution systems.Owing to the difficulties inherent in realizing a high-efficiency fiber homodyne detector,challenges still exist in continuous-variable measurement-device-independent quantum key distribution system implementation.We offer an alternative approach in an attempt to solve these difficulties and improve the potential for system implementation.Here,a novel practical detector modeling method is utilized,which is combined with a one-time shot-noise-unit calibration method for the purpose of system realization.The new modeling method benefits greatly from taking advantage of one-time shot-noise-unit calibration methods,such as measuring electronic noise and shot noise directly to a novel shot-noise unit,so as to eliminate the statistical fluctuations found in previous methods;this makes the implementation of such systems simpler,and the calibration progress more accurate.We provide a simulation of the secret key rate versus distance with different parameters.In addition,the minimal detection efficiency required at each distance,as well as the contrast between the two methods,are also shown,so as to provide a reference in terms of system realization.

3D-printed models improve surgical planning for correction of severe postburn ankle contracture with an external fixator

Gradual distraction with an external fixator is a widely used treatment for severe postburn ankle contracture(SPAC).However,application of external fixators is complex,and conventional two-dimensional(2D)imaging-based surgical planning is not particularly helpful due to a lack of spatial geometry.The purpose of this study was to evaluate the surgical planning process for this procedure with patient-specific three-dimension-printed models(3DPMs).In this study,patients coming from two centers were divided into two cohorts(3DPM group vs.control group)depending on whether a 3DPM was used for preoperative surgical planning.Operation duration,improvement in metatarsal-tibial angle(MTA),range of motion(ROM),the American Orthopedic Foot and Ankle Society(AOFAS)scores,complications,and patient-reported satisfaction were compared between two groups.The 3DPM group had significantly shorter operation duration than the control group((2.0±0.3)h vs.(3.2±0.3)h,P<0.01).MTA,ROM,and AOFAS scores between the two groups showed no significant differences pre-operation,after the removal of the external fixator,or at follow-up.Plantigrade feet were achieved and gait was substantially improved in all patients at the final follow-up.Pin-tract infections occurred in two patients(one in each group)during distraction and were treated with wound care and oral antibiotics.Patients in the 3DPM group reported higher satisfaction than those in the control group,owing to better patient-surgeon communication.Surgical planning using patient-specific 3DPMs significantly reduced operation duration and increased patient satisfaction,while providing similar improvements in ankle movement and function compared to traditional surgical planning for the correction of SPAC with external fixators.