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Scientific Reports

A clock synchronization method based on quantum entanglement

Jianxin Shi, Shanshan Shen

Published Jun 17, 2022• 22 citations
Publisher

Abstract

This study presents a clock synchronization method based on quantum entanglement which is simple and reliable and more efficient. The clock synchronization method based on quantum entanglement scheme can greatly improve the accuracy and precision of measurement. More importantly, the proposed method avoids synchronization error caused by traditional method due to the asymmetry of two-way delay. The probability of measuring the quantum state oscillates in cosine or sine fashion with propagation delay. The final experimental and simulation results are basically consistent with the theoretical results. The clock synchronization method based on quantum entanglement scheme can greatly imrprove the accuracy and precision of measurement.

DOI
10.1038/s41598-022-14087-z

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This study presents a clock synchronization method based on quantum entanglement which is simple and reliable and more efficient. The clock synchronization method based on quantum entanglement scheme can greatly improve the accuracy and precision of measurement. More importantly, the proposed method avoids synchronization error caused by traditional method due to the asymmetry of two-way delay. The probability of measuring the quantum state oscillates in cosine or sine fashion with propagation delay. The final experimental and simulation results are basically consistent with the theoretical results. The clock synchronization method based on quantum entanglement scheme can greatly imrprove the accuracy and precision of measurement.
The synchronization of distant clocks is of considerable importance for many practical and scientific applications. The new protocol for clock synchronization based on quantum theory is proposed in this paper. The experiment framework mostly same as Mach-Zehnder interferometer. We can determine the time difference through exchange of each other's photons .The main features of this scheme is of need not transfer a real hardware clock or measure any time during the synchronization. Compare with classical methods, this protocol is not limited by any dispersion and gravitational potential that maybe present in the propagation. So the ping-pong protocol can achieve more precision than classical methods. The new one's precision is related with the number of circulation in the experimentation.
Quantum clock synchronization schemes utilizing frequency-entangled pulses have flourished for their potentially superior precision to the classical protocols. In this Letter, a new experimental record based on the second-order quantum interference algorithm is reported, to the best of our knowledge. The synchronization accuracy between two parties separated by a 6 km fiber coiling link, which is evaluated by the time offset shift relative to that with the fibers removed, has been measured to be 13±1 ps. The stability in terms of time deviation (TDEV) of 0.81 ps at an averaging time of 100 s has been achieved. The long-term synchronization stability is seen determined by the measurement device, and a minimum stability of 60 fs has been reached at 25,600 s. Furthermore, for the first time to the best of our knowledge, we quantify the performance of this quantum synchronization scheme, and very good agreements with the experimental results have been achieved. According to the quantum simulation, further improvements for both the synchronizing stability and accuracy can be expected.
This paper presents a novel algorithm for ultra-high-precision synchronization based on quantum entanglement. Traditional synchronization methods rely on classical measurement, which introduces inherent errors and limitations in achieving accurate time synchronization. This work introduces a new approach that leverages the unique properties of quantum entanglement to dramatically enhance synchronization precision and robustness. The core mechanism involves establishing and maintaining entangled states between multiple particles to facilitate precise temporal correlation. This algorithm demonstrates significantly improved accuracy and stability compared to existing synchronization techniques, offering a potential advancement in precision measurement and synchronization applications.
Quantum clock synchronization (QCS) aims to establish a shared temporal reference between distant nodes by exploiting uniquely quantum phenomena such as entanglement, single-photon interference, and quantum correlations. In contrast to classical synchronization and time-transfer techniques, which are limited by signal propagation delays, atmospheric disturbances, and oscillator drift, QCS protocols offer the potential to surpass classical precision bounds and enhance resilience against adversarial manipulations. As precise and secure time synchronization underpins distributed quantum networks, navigation systems, and emerging quantum Internet infrastructures, understanding QCS principles, capabilities, and implementation challenges has become increasingly important. This survey provides a unified and critical overview of the rapidly growing QCS research landscape, highlighting fundamentals, protocol types, enabling resources, performance constraints, security considerations, and practical implementations of QCS. We first introduce the theoretical underpinnings of QCS, including entanglement-assisted time transfer, Hong-Ou-Mandel interference-based synchronization, and quantum slow-clock transport. We then categorize the main QCS protocols, ranging from ticking-qubit and entanglement-based schemes to time-of-arrival correlation methods, conveyor-belt synchronization, and quantum-enhanced two-way time transfer. This organization clarifies the relationships between protocol families and their achievable precision advantages over classical methods. Key quantum resources such as spontaneous parametric down-conversion-based entangled photon pairs, Greenberger-Horne-Zeilinger and W multipartite states, squeezed and frequency-entangled light, quantum frequency combs, and quantum memories are reviewed in the context of scalability and robustness.
The time synchronization accuracy on the order of nanoseconds can be provided using the conventional methods of time synchronization,a higher measurement accuracy on the order of femto-seconds can be reached by quantum measurement which employs entangled photon pairs in order to break the limit of measurement accuracy of conventional methods.The second-order correlation function of the entangled photon pairs which produced in a spontaneous type?Ⅱparametric down-conversion is investigated by integral transforming in the nonlinear crystal and substituting the first order expand of the wave vector.The relation between the second-order correlation function and temporal difference.A quantum method in clock synchronization between satellite and ground station is proposed based on the temporal correlation.The simulation indicates that the measurement accuracy provided by the second-order correlation function can be 70femto-seconds and the synchronization accuracy in the scheme can be 140femto-seconds in the ideal case.