For the high precision time synchronization demand of ships, advantages and disadvantages of the present time transfer methods are analyzed, the two-way microwave time transfer （TWMTT） method is adopted to resolve t...For the high precision time synchronization demand of ships, advantages and disadvantages of the present time transfer methods are analyzed, the two-way microwave time transfer （TWMTT） method is adopted to resolve the time synchronization problem in the Naval Ship Formation. After expounding the principle and system composition of TWMTT method, the various factors influencing the synchronous precision are analyzed, such as time-interval measurement error, TWMTT equipment delay error, signal propagation error in air, and signal delay error caused by shipping. To improve the time synchronization precision, all the error sources above are deduced with mathematical measures to definite the critical one, and the signal processing measures such as Pseudo code spread spectrum time comparison signal generation technology, FFT fast acquisition technology and precise tracking technology are used into the modem which is the core equipment of the TWMTT. And, calibration method of TWMTT equipment delay are developed. Through theoretical a- nalysis and simulation verification, the precision of shipboard two-way microwave time synchroniza- tion can reach 1 ns.展开更多
To meet the needs of signal alignment between the transmitter and receiver in a quantum key distribution(QKD) system, we put forward a TDC-GPX-based synchronization scheme, which is based on high-precision time measur...To meet the needs of signal alignment between the transmitter and receiver in a quantum key distribution(QKD) system, we put forward a TDC-GPX-based synchronization scheme, which is based on high-precision time measurement. We send a low-frequency repeat optical pulse synchronized with associated quantum signals on the receiver's side by using a time-to-digital converter(TDC)module, the time intervals between quantum signals, and synchronization signals measured and converted to corresponding temporal orders to complete the synchronization.We state the principle of the synchronization scheme in detail and then verify it in an actual QKD test bed. The test results show that our TDC-GPX-based synchronization can obtain a time resolution better than 100 ps, and the proposed scheme shows full feasibility for an actual QKD system.展开更多
Precision time synchronization underpins a wide array of modern technologies,from relativistic geodesy to distributed quantum networks.Quantum two-way time transfer(QTWTT),which harnesses the tight temporal correlatio...Precision time synchronization underpins a wide array of modern technologies,from relativistic geodesy to distributed quantum networks.Quantum two-way time transfer(QTWTT),which harnesses the tight temporal correlations of energy-time entangled photon pairs,has achieved remarkable sub-picosecond stability[1]while offering intrinsic security against timing attacks[2].Yet,the quantum nocloning theorem—prohibiting the amplification of quantum states—imposes a fundamental barrier to extending QTWTT over long distances due to inevitable signal loss in fiber-optic channels[3].In a recent study published in Science China Physics,Mechanics&Astronomy,a cascaded Q-TWTT architecture is presented that bypasses this challenge by using relay stations to generate and distribute entangled photon pairs[4].展开更多
Quantum two-way time transfer(Q-TWTT)leveraging energy-time entangled biphotons has achieved sub-picosecond stability but faces fundamental distance limitations due to the no-cloning theorem’s restriction on quantum ...Quantum two-way time transfer(Q-TWTT)leveraging energy-time entangled biphotons has achieved sub-picosecond stability but faces fundamental distance limitations due to the no-cloning theorem’s restriction on quantum amplification.To overcome this challenge,we propose a cascaded Q-TWTT architecture employing relay stations that generate and distribute new energy-time entangled biphotons after each transmission segment.Theoretical modeling reveals sublinear standard deviation growth(merely\√N×increase for N×equidistant segments),enabling preservation of sub-picosecond stability over extended distances.We experimentally validate this approach using a three-station cascaded configuration over 2×100 km fiber segments,demonstrating strong agreement with theory.Utilizing independent Rb clocks at end and relay stations with online frequency skew correction,we achieve time stabilities of 3.82 ps at 10 s and 0.39 ps at 5120 s.The consistency in long-term stability between cascaded and single-segment configurations confirms high-precision preservation across modular quantum networks.This work establishes a framework for long-distance quantum time transfer that bypasses the no-cloning barrier,providing a foundation for future quantum-network timing infrastructure.展开更多
The process to achieve time synchronization and ranging for a network of mobile nodes is raising a concern among researchers, and hence a variety of joint time synchronization and ranging algorithms have been proposed...The process to achieve time synchronization and ranging for a network of mobile nodes is raising a concern among researchers, and hence a variety of joint time synchronization and ranging algorithms have been proposed in recent years. However, few of them handle the case of all-node motion under unknown positions and velocities. This study addresses the problem of determining ranging and time synchronization for a group of nodes moving within a local area. First, we examined several models of clock discrepancy and synchronous two-way ranging. Based upon these models, we present a solution for time synchronization with known positions and velocities. Next, we propose a functional model that jointly estimates the clock skew, clock offset, and time of flight in the absence of a priori knowledge for a pair of mobile nodes. Then, we extend this model to a network-wide time synchronization scheme by way of a global least square estimator. We also discuss the advantages and disadvantages of our model compared to the existing algorithms, and we provide some applicable scenarios as well. Finally, we show that the simulation results verify the validity of our analysis.展开更多
基金Supported by the Ministerial Level Foundation(2102812)
文摘For the high precision time synchronization demand of ships, advantages and disadvantages of the present time transfer methods are analyzed, the two-way microwave time transfer （TWMTT） method is adopted to resolve the time synchronization problem in the Naval Ship Formation. After expounding the principle and system composition of TWMTT method, the various factors influencing the synchronous precision are analyzed, such as time-interval measurement error, TWMTT equipment delay error, signal propagation error in air, and signal delay error caused by shipping. To improve the time synchronization precision, all the error sources above are deduced with mathematical measures to definite the critical one, and the signal processing measures such as Pseudo code spread spectrum time comparison signal generation technology, FFT fast acquisition technology and precise tracking technology are used into the modem which is the core equipment of the TWMTT. And, calibration method of TWMTT equipment delay are developed. Through theoretical a- nalysis and simulation verification, the precision of shipboard two-way microwave time synchroniza- tion can reach 1 ns.
基金supported by National Natural Science Foundation of China (Nos. 11375195, 11375263 and 11105143)National Magnetic Confinement Fusion Energy Development Research (No. 2013GB104003)
文摘To meet the needs of signal alignment between the transmitter and receiver in a quantum key distribution(QKD) system, we put forward a TDC-GPX-based synchronization scheme, which is based on high-precision time measurement. We send a low-frequency repeat optical pulse synchronized with associated quantum signals on the receiver's side by using a time-to-digital converter(TDC)module, the time intervals between quantum signals, and synchronization signals measured and converted to corresponding temporal orders to complete the synchronization.We state the principle of the synchronization scheme in detail and then verify it in an actual QKD test bed. The test results show that our TDC-GPX-based synchronization can obtain a time resolution better than 100 ps, and the proposed scheme shows full feasibility for an actual QKD system.
文摘Precision time synchronization underpins a wide array of modern technologies,from relativistic geodesy to distributed quantum networks.Quantum two-way time transfer(QTWTT),which harnesses the tight temporal correlations of energy-time entangled photon pairs,has achieved remarkable sub-picosecond stability[1]while offering intrinsic security against timing attacks[2].Yet,the quantum nocloning theorem—prohibiting the amplification of quantum states—imposes a fundamental barrier to extending QTWTT over long distances due to inevitable signal loss in fiber-optic channels[3].In a recent study published in Science China Physics,Mechanics&Astronomy,a cascaded Q-TWTT architecture is presented that bypasses this challenge by using relay stations to generate and distribute entangled photon pairs[4].
基金supported by the National Natural Science Foundation of China(Grant Nos.12033007,12103058,12203058,and 12074309)the Youth Innovation Promotion Association of the Chinese Academy of Sciences(Grant Nos.2021408,2022413,and 2023425)the Innovation Program for Quantum Science and Technology(Grant No.2021ZD0300900).
文摘Quantum two-way time transfer(Q-TWTT)leveraging energy-time entangled biphotons has achieved sub-picosecond stability but faces fundamental distance limitations due to the no-cloning theorem’s restriction on quantum amplification.To overcome this challenge,we propose a cascaded Q-TWTT architecture employing relay stations that generate and distribute new energy-time entangled biphotons after each transmission segment.Theoretical modeling reveals sublinear standard deviation growth(merely\√N×increase for N×equidistant segments),enabling preservation of sub-picosecond stability over extended distances.We experimentally validate this approach using a three-station cascaded configuration over 2×100 km fiber segments,demonstrating strong agreement with theory.Utilizing independent Rb clocks at end and relay stations with online frequency skew correction,we achieve time stabilities of 3.82 ps at 10 s and 0.39 ps at 5120 s.The consistency in long-term stability between cascaded and single-segment configurations confirms high-precision preservation across modular quantum networks.This work establishes a framework for long-distance quantum time transfer that bypasses the no-cloning barrier,providing a foundation for future quantum-network timing infrastructure.
基金supported by the National Natural Science Foundation of China(Grant No.61471021)
文摘The process to achieve time synchronization and ranging for a network of mobile nodes is raising a concern among researchers, and hence a variety of joint time synchronization and ranging algorithms have been proposed in recent years. However, few of them handle the case of all-node motion under unknown positions and velocities. This study addresses the problem of determining ranging and time synchronization for a group of nodes moving within a local area. First, we examined several models of clock discrepancy and synchronous two-way ranging. Based upon these models, we present a solution for time synchronization with known positions and velocities. Next, we propose a functional model that jointly estimates the clock skew, clock offset, and time of flight in the absence of a priori knowledge for a pair of mobile nodes. Then, we extend this model to a network-wide time synchronization scheme by way of a global least square estimator. We also discuss the advantages and disadvantages of our model compared to the existing algorithms, and we provide some applicable scenarios as well. Finally, we show that the simulation results verify the validity of our analysis.
