arXiv:2111.00380

Demonstration of 50 km Fiber-optic two-way quantum time transfer at femtosecond-scale precision

Huibo Hong, Runai Quan, Xiao Xiang, Wenxiang Xue, Honglei Quan, Wenyu Zhao, Yuting Liu, Mingtao Cao, Tao Liu, Shougang Zhang, Ruifang Dong

Published Oct 31, 2021• 1 citation

arXiv HTML PDF

Abstract

The two-way quantum time transfer method has been proposed and experimentally demonstrated for its potential enhancements in precision and better guarantee of security. To further testify its advantage in practical applications, the applicable direct transmission distance as well as the achievable synchronization precision between independent time scales is of great interest. In this paper, an experiment on two-way quantum time transfer has been carried out over a 50 km long fiber link. With the common clock reference, a short-term stability of 2.6 ps at an averaging time of 7 s and a long-term stability of 54.6 fs at 57300 s were obtained. With independent clock references, assisted by microwave frequency transfer technology, the achieved synchronization showed almost equal performance and reached a stability of 89.5 fs at 57300 s. Furthermore, the spectral consistency of the utilized entangled photon pair sources has been studied concerning its effect on the transfer accuracy and long-term stability. The results obtained have promised a bright future of the two-way quantum time transfer for realizing high-precision time synchronization on metropolitan area fiber links.

DOI: 10.48550/arxiv.2111.00380

Related papers

Demonstration of 50 Km Fiber-Optic Two-Way Quantum Clock Synchronization

Huibo Hong, Runai Quan, Xiao Xiang +8 more

Fiber-optic Quantum clock synchronization has been proposed and experimentally demonstrated for its potential enhancements in precision and better guarantee of security. To further prove its advantage in practical applications, it is necessary to test its synchronization performance between clocks apart for at least intracity optical fiber distance. In this paper, we report a fiber-optic two-way quantum clock synchronization experiment with the distance reaching 50 km. With the common reference clock, a synchronization stability of 54.6 fs at 57300 s and an accuracy of 1.3 ps±36.6 ps have been achieved. With independent reference clocks, comparable performance has also been achieved combined with the microwave frequency transfer technology, which shows a stability of 89.5 fs at 57300 s. These results nicely showcase the feasibility of the two-way quantum clock synchronization to provide femtosecond-scale synchronization precision over intracity optical fiber links.

Journal of Lightwave TechnologyFeb 23, 202232 citations

A 50 km fiber-optic two-way quantum time transfer experiment with long-term stability below 100 fs

Huibo Hong, Ruiai Quan, Xiao Xiang +7 more

Based on frequency entangled sources and arrival time measurements, a best time synchronization stability result of fewer than 100 fs has been reported over 20km fiber links, verifying the superiority of quantum time synchronization. In this paper, a two-way quantum time transfer over 50 km fiber links with the same frequency standard was implemented, with a short-term stability of 2.63 ps at an averaging time of 18 s and a long-term stability of 79.2 fs at 73700 s. The system accuracy in terms of the 50km fiber transfer length is measured as 524.75 ps, the agreement of which with the theoretical simulation illustrates that improving the spectral consistency of the two entangled sources will significantly improve the accuracy. This result shows that the fiber-optic two-way quantum time transfer can be successfully extended to a metropolitan fiber link distance of around 50 km or longer, not only maintaining the transfer stability well below picosecond but also promising further improvements in synchronization accuracy.

Real-time Photonic Measurements, Data Management, and ProcessingOct 9, 20211 citation

Fiber-optic two-way quantum time transfer with frequency-entangled pulses

Feiyan Hou, Runai Quan, Ruifang Dong +8 more

High-precision time transfer is of fundamental interest in physics and metrology. Quantum time transfer technologies that use frequency-entangled pulses and their coincidence detection have been proposed, offering potential enhancements in precision and better guarantees of security. In this paper, we describe a fiber-optic two-way quantum time transfer experiment. Using quantum nonlocal dispersion cancellation, time transfer over a 20-km fiber link achieves a time deviation of 922 fs over 5 s and 45 fs over 40 960 s. The time transfer accuracy as a function of fiber lengths from 15 m to 20 km is also investigated, and an uncertainty of 2.46 ps in standard deviation is observed. In comparison with its classical counterparts, the fiber-optic two-way quantum time transfer setup shows appreciable improvement, and further enhancements could be obtained by using new event timers with subpicosecond precision and single-photon detectors with lower timing jitter for optimized coincidence detection. Combined with its security advantages, the femtosecond-scale two-way quantum time transfer is expected to have numerous applications in high-precision middle-haul synchronization systems.

arXiv:1812.10077Physical Review AAug 29, 201946 citations

Quantum Two-Way Time Transfer Over a 103 km Urban Fiber

Huibo Hong, Runai Quan, Xiao Xiang +5 more

As a new approach to realizing high-precision time synchronization between remote time scales, quantum two-way time transfer via laboratory fiber link has shown significant enhancement of the transfer stability to several tens of femtoseconds. To verify its great potential in practical systems, the field test in long-haul installed fiber optic infrastructure is required to be demonstrated. In this article, we implement the two-way quantum time transfer over a 103 km urban fiber link. A time transfer stability of 3.67 ps at 10 s and 0.28 ps at 40 000 s has been achieved, despite the large attenuation of 38 dB leading to fewer than 40 correlated events per second. This achievement marks the first successful step of quantum two-way time transfer in the task of high-precision long-distance field transfer systems.

arXiv:2305.01897Journal of Lightwave TechnologyOct 10, 202324 citations

Implementation of field two-way quantum synchronization of distant clocks across a 7 km deployed fiber link

Runai Quan, Huibo Hong, Wenxiang Xue +8 more

The two-way quantum clock synchronization has been shown to provide femtosecond-level synchronization capability and security against symmetric delay attacks, thus becoming a prospective method to compare and synchronize distant clocks with enhanced precision and safety. In this letter, a field test of two-way quantum synchronization between a H-maser and a Rb clock linked by a 7 km-long deployed fiber is implemented by using time-energy entangled photon-pair sources. Limited by the intrinsic frequency stability of the Rb clock, the achieved time stability at 30 s is measured as 32 ps. By applying a fiber-optic microwave frequency transfer technology to build frequency syntonization between the separated clocks, the limit set by the intrinsic frequency stability of the Rb clock is overcome. A significantly improved time stability of 1.9 ps at 30 s is achieved, which is mainly restrained by the low number of acquired photon pairs due to the low sampling rate of the utilized coincidence measurement system. Such implementation demonstrates the high practicability of the two-way quantum clock synchronization method for promoting field applications.

arXiv:2109.00784Optics ExpressMar 7, 202230 citations

Development of prototype system for quantum two-way clock synchronization

Bingke Shi, Xiao Xiang, Huibo Hong +7 more

In this Letter, we report a prototype system that realizes the complete functionality for quantum two-way time transfer, comparison, and synchronization between two integrated terminals. The synchronization performance was tested over a 50-km spooled fiber link. With the common frequency reference, the time deviation was measured as 0.45 ps at an averaging time of 104 s, which is limited by the system's hardware and determines the minimum achievable synchronization stability. By employing an open-loop fiber-optic microwave frequency transfer in combination with the technique of dynamically identifying and steering the time offset between the terminals, a synchronization stability of 1.26 ps at 104 s was achieved. Further utilizing the grey prediction model to correct the time offset data, the synchronization stability was significantly improved to 0.69 ps at 104 s, showing its potential to enhance the synchronization performance. This report marks the development of a utility quantum two-way clock synchronization system. The ongoing exploration of advanced time-offset adjustment strategies to attain synchronization stability significantly below 1 ps is poised to yield invaluable benefits for future applications.

Applied Physics LettersMar 4, 20249 citations