Experimental Research On Laser Time Transfer Based On Micius Satellite

Time(frequency)is one of the basic physical quantities,and many physical quan-tities are related to it.With the development of ultra-high precision clocks,the stability of optical clock in the laboratory has reached the order of 10-18 and moves towards the 10-19 level.Moreover,a cold atomic clock with a stability of 7.2 × 10-16 has been tested in space recently.High-precision time and frequency transfer over long-distance in free-space link have very important applications in many areas such as precision measurement,fundamental physics,deep space exploration,geophysics,satellite nav-igation and so on.However,the daily stability of time and frequency transfer based on microwave technology is on the order of 10-15,so a higher precision time and fre-quency transfer method is needed.On the other hand,time synchronization is also the cornerstone of military,industry,telecommunication and financial networks,which are concerned about the national security and people's livelihood.Unfortunately,there are many security issues exist in the time synchronization schemes which are widely used today.With the development of quantum information technology,it provides a new perspective for solving these problems.The Micius satellite has achieved a series of progress in the quantum physics experiments at space scale.Its optical resources also provide a good platform for laser time transfer experiments.Based on the Micius satel-lite,this thesis conducts experimental research on laser time transfer,and explores the realization of higher precision and safer time transfer.In terms of high precision,a systematic analysis of the asynchronous two-way laser time transfer scheme is carried out to demonstrate that the scheme can achieve time transfer with the daily stability of 10-17,and a series of verification experiments are carried out based on the Micius satellite.We use the existing resources of the Mi-cius satellite to establish asynchronous two-way optical links and satellite common-view links.With a high sampling rate,the asynchronous two-way optical links have achieved normal point precision of 30ps for time transfer and 1cm for ranging.This experiment achieved the best level of laser time transfer between satellite and ground,and verified the feasibility of this scheme and its applications in space.Besides,we also propose a laser time transfer scheme based on satellite common-view,which has two implementations with one-way or two-way links.Based on the Micius satellite,we performed a zero-baseline common-view time transfer experiment,achieving a time comparison precision of 25ps and a short-term stability of 5ps@12.6s.It shows the common-view scheme have a good system performance.In addition,we also conducted a 1200-kilometer baseline time comparison demonstration between Delingha and Li-jiang,laying the foundation for high-orbit satellite common-view laser time transfer in future.In terms of security,the security of time transfer and the necessary conditions for implementing secure time transfer are analyzed and discussed.According to the cur-rent quantum information technology,a secure time transfer scheme based on two-way quantum key distribution is proposed.A key technical verification experiment was car-ried out between the Micius satellite and the ground station for secure time transfer.We use the quantum key distribution link from the Micius and the pulsed laser link from the ground to form asynchronous two-way time transfer.We realized secure data transmis-sion in the experiment by encryption the time data with secure key which generated by the satellite-to-ground quantum key distribution.In this experiment,we verified several key technologies such as using secure quantum signals for time transfer and secure data transmission.The results show that in the future,it is possible to achieve nanosecond-level secure time transfer based on this scheme.These research work promote the applications of high-precision laser time transfer in space and provide a new solution for security time transfer.In the future,a higher-precision and safer time and frequency network can be constructed in space.The main innovations of this paper are:1.Based on asynchronous two-way laser links between the Micius satellite and ground,a time comparison precision of approximately 30ps is achieved which is the best level of current laser time transfer precision between satellite and ground.This scheme has a small link attenuation and is suitable for high-precision time transfer in free-space over long distances.2.A laser time transfer scheme based on satellite common-view is proposed.We performed a zero-baseline common-view time transfer experiment based on the Micius satellite,and achieved a time comparison precision of 25ps and a short-term stability of 5ps@12.6s.This work lay the foundation for high-orbit satellite common-view laser time transfer in future.3.A secure time transfer scheme based on two-way quantum key distribution is proposed,and a key technology verification experiment is carried out based on the Micius satellite.It shows that the secure time transfer at the nanosecond level is possible.Combined with quantum communication networks,a safer time transfer network can be built in the future.