To realize practical wide-area quantum communication,a satellite-to-ground network with partially entangled states is developed in this paper.For efficiency and security reasons,the existing method of quantum communic...To realize practical wide-area quantum communication,a satellite-to-ground network with partially entangled states is developed in this paper.For efficiency and security reasons,the existing method of quantum communication in distributed wireless quantum networks with partially entangled states cannot be applied directly to the proposed quantum network.Based on this point,an efficient and secure quantum communication scheme with partially entangled states is presented.In our scheme,the source node performs teleportation only after an end-to-end entangled state has been established by entanglement swapping with partially entangled states.Thus,the security of quantum communication is guaranteed.The destination node recovers the transmitted quantum bit with the help of an auxiliary quantum bit and specially defined unitary matrices.Detailed calculations and simulation analyses show that the probability of successfully transferring a quantum bit in the presented scheme is high.In addition,the auxiliary quantum bit provides a heralded mechanism for successful communication.Based on the critical components that are presented in this article an efficient,secure,and practical wide-area quantum communication can be achieved.展开更多
The laser beam used to establish a communication channel between satellite and ground segments has a small divergence angle and a tiny spot on the Earth's surface,which may lead to the fail of the system.So it'...The laser beam used to establish a communication channel between satellite and ground segments has a small divergence angle and a tiny spot on the Earth's surface,which may lead to the fail of the system.So it's important to study the deflection of laser beam by the Earth's atmosphere and find a way to calibrate this error.Both theoretical analysis and real data processing method are used to obtain the mathematical model for divergence angle of laser communication beam and its correction function.Then the model has been applied to the data,which was used to describe the atmosphere state by traditional ground segments to obtain the critical elevation angle.According to the results of calculation,our conclusion will be that the correction should be done when the critical elevation happens.展开更多
Orthogonal time frequency space(OTFS)modulation has been widely considered for high-mobility scenarios.Satellite-to-ground communications have recently received much attention as a typical high-mobility scenario and f...Orthogonal time frequency space(OTFS)modulation has been widely considered for high-mobility scenarios.Satellite-to-ground communications have recently received much attention as a typical high-mobility scenario and face great challenges due to the high Doppler shift.To enable reliable communications and high spectral efficiency in satellite mobile communications,we evaluate OTFS modulation performance for geostationary Earth orbit and low Earth orbit satellite-to-ground channels at sub-6-GHz and millimeter-wave bands in both lineof-sight and non-line-of-sight cases.The minimum mean squared error with successive detection(MMSE-SD)is used to improve the bit error rate performance.The adaptability of OTFS and the signal detection technologies in satellite-to-ground channels are analyzed.Simulation results confirm the feasibility of applying OTFS modulation to satellite-to-ground communications with high mobility.Because full diversity in the delay-Doppler domain can be explored,different terminal movement velocities do not have a significant impact on the performance of OTFS modulation,and OTFS modulation can achieve better performance compared with classical orthogonal frequency division multiplexing in satellite-to-ground channels.It is found that MMSE-SD can improve the performance of OTFS modulation compared with an MMSE equalizer.展开更多
基金supported by the National Natural Science Foundation of China(Grant Nos.61072067 and 61372076)the 111 Project(Grant No.B08038)+1 种基金the Fund from the State Key Laboratory of Integrated Services Networks(Grant No.ISN 1001004)the Fundamental Research Funds for the Central Universities(Grant Nos.K5051301059 and K5051201021)
文摘To realize practical wide-area quantum communication,a satellite-to-ground network with partially entangled states is developed in this paper.For efficiency and security reasons,the existing method of quantum communication in distributed wireless quantum networks with partially entangled states cannot be applied directly to the proposed quantum network.Based on this point,an efficient and secure quantum communication scheme with partially entangled states is presented.In our scheme,the source node performs teleportation only after an end-to-end entangled state has been established by entanglement swapping with partially entangled states.Thus,the security of quantum communication is guaranteed.The destination node recovers the transmitted quantum bit with the help of an auxiliary quantum bit and specially defined unitary matrices.Detailed calculations and simulation analyses show that the probability of successfully transferring a quantum bit in the presented scheme is high.In addition,the auxiliary quantum bit provides a heralded mechanism for successful communication.Based on the critical components that are presented in this article an efficient,secure,and practical wide-area quantum communication can be achieved.
基金Supported by the Strategic Priority Research Program of Chinese Academy of Sciences(XDA04080201)。
文摘The laser beam used to establish a communication channel between satellite and ground segments has a small divergence angle and a tiny spot on the Earth's surface,which may lead to the fail of the system.So it's important to study the deflection of laser beam by the Earth's atmosphere and find a way to calibrate this error.Both theoretical analysis and real data processing method are used to obtain the mathematical model for divergence angle of laser communication beam and its correction function.Then the model has been applied to the data,which was used to describe the atmosphere state by traditional ground segments to obtain the critical elevation angle.According to the results of calculation,our conclusion will be that the correction should be done when the critical elevation happens.
基金Project supported by the National Key R&D Program of China(No.2020YFB1806903)the National Natural Science Foundation of China(Nos.61922012,62001519,52042201,U1834210,and 61961130391)+2 种基金the State Key Laboratory of Rail Traffic Control and Safety,China(Nos.RCS2020ZT008,RCS2019ZZ007,and RCS2020ZT010)the Teaching Reform Project,China(No.134811522)the Fundamental Research Funds for the Central Universities,China(Nos.2020JBZD005 and I20JB0200030)。
文摘Orthogonal time frequency space(OTFS)modulation has been widely considered for high-mobility scenarios.Satellite-to-ground communications have recently received much attention as a typical high-mobility scenario and face great challenges due to the high Doppler shift.To enable reliable communications and high spectral efficiency in satellite mobile communications,we evaluate OTFS modulation performance for geostationary Earth orbit and low Earth orbit satellite-to-ground channels at sub-6-GHz and millimeter-wave bands in both lineof-sight and non-line-of-sight cases.The minimum mean squared error with successive detection(MMSE-SD)is used to improve the bit error rate performance.The adaptability of OTFS and the signal detection technologies in satellite-to-ground channels are analyzed.Simulation results confirm the feasibility of applying OTFS modulation to satellite-to-ground communications with high mobility.Because full diversity in the delay-Doppler domain can be explored,different terminal movement velocities do not have a significant impact on the performance of OTFS modulation,and OTFS modulation can achieve better performance compared with classical orthogonal frequency division multiplexing in satellite-to-ground channels.It is found that MMSE-SD can improve the performance of OTFS modulation compared with an MMSE equalizer.