Telecom standards efficiently enable time synchronization mechanisms in multi-node Quantum Networks (QNs) by combining Synchronous Ethernet (SyncE) and Precision Time Protocol (PTP). The architecture explored in this work utilizes SyncE to provide all connected nodes with a stable and precise frequency reference, adjustable in the range from 1 Hz to 125MHz, obtaining sub-nanosecond temporal jitter in the real-time/quantum plane. This reference is complemented with PTP to provide a distributed time reference for synchronization with a microsecond-level temporal allocation capability. In particular, in the control plane, PTP enables time division multiple access (TDMA) for sharing the quantum channel in multi-node quantum networks QNs. It is demonstrated that the proposed architecture achieves nanosecond synchronous transfer in the real-time/quantum plane and allocates microsecond time windows through the control plane. The theoretical model and experimental results validate performing common quantum communications operations with 98% fidelity and 10−2quantum bit error rate (QBER) at an emission rate of 12.5 Mqb/s. The results confirm that SyncE/PTP synchronization is a viable and scalable solution for future multi-node QN infrastructures.
Telecom standards efficiently enable time synchronization mechanisms in multi-node Quantum Networks (QNs) by combining Synchronous Ethernet (SyncE) and Precision Time Protocol (PTP). The architecture explored in this work utilizes SyncE to provide all connected nodes with a stable and precise frequency reference, adjustable in the range from 1 Hz to 125MHz, obtaining sub-nanosecond temporal jitter in the real-time/quantum plane. This reference is complemented with PTP to provide a distributed time reference for synchronization with a microsecond-level temporal allocation capability. In particular, in the control plane, PTP enables time division multiple access (TDMA) for sharing the quantum channel in multi-node quantum networks QNs. It is demonstrated that the proposed architecture achieves nanosecond synchronous transfer in the real-time/quantum plane and allocates microsecond time windows through the control plane. The theoretical model and experimental results validate performing common quantum communications operations with 98% fidelity and 10−2quantum bit error rate (QBER) at an emission rate of 12.5 Mqb/s. The results confirm that SyncE/PTP synchronization is a viable and scalable solution for future multi-node QN infrastructures.
Accurate time and phase distribution remain central requirements for emerging communication systems, where synchronization affects radio coordination, fronthaul stability, and network-based positioning. Current approaches rely heavily on GNSS, the Precision Time Protocol (PTP), and Synchronous Ethernet (SyncE). Still, their performance is limited by delay asymmetry, accumulated jitter across long paths, and GNSS's vulnerability to blockage or interference. Recent progress in optical and quantum time-transfer techniques, particularly time-correlated entangled photons (TCEP) and optical lattice clocks (OLCs), offers an opportunity to improve both stability and calibration accuracy. This work proposes a practical synchronization framework that integrates OLC-based time references, TCEP-assisted calibration between core nodes, and standards-compliant packet-based delivery using PTP/SyncE in accordance with ITU-T G.8271. We describe how to interface photonic subsystems, FPGA-based timestamping hardware, and telecom boundary clocks without modifying existing radio functions. We also evaluate how improved synchronization propagates to key applications: uplink and downlink TDoA positioning, fronthaul and TSN timing stability, and NTN deployments where GNSS is unreliable. The architecture is designed for incremental deployment and aligns with current operational practices.
The advent of Beyond 5G (emerging 6G) technologies represents a significant step forward in telecommunications, offering unprecedented data speeds and connectivity. These advances enable a wide range of applications, from enhanced mobile broadband and the Internet of Things to ultra-reliable low-latency communication and the tactical Internet. Thus, having accurate and dependable time synchronization is of utmost importance and plays a critical role in ensuring that all processes function smoothly and effectively. However, existing standards, such as the precision time protocol, are unreliable due to jitters, datagram losses, and complexity. Increasing the synchronization error from the ideal tens of nanoseconds to hundreds of microseconds is unacceptable in future-generation networks. This work provides a novel way to establish ultraprecise synchronization, which is critical for the growth of converged optical communication networks and the 6G era. We investigate quantum non-linear synchronization (QNS), which explores the interaction between the non-linear dynamics of atomic systems and dissipation to establish a stable limit-cycle state. In this process, atoms confined within optical resonators are subjected to potential fields, and their spatial motion is synchronized by achieving a stable, phase-locked configuration. By introducing photons into the optical resonators and precisely managing the dissipation effects, it is possible to synchronize multiple optical resonators (referred to as nodes), even in systems with more than three interconnected resonators containing non-linear atoms. To transcend the synchronization signal from the optical setup to communication networks, we propose a distinct mechanism that utilizes the exceptional precision of QNS in the optical lattice setup and frequency down-conversion using frequency combs. In addition, it is combined with electronic components such as analog-to-digital converters and field-programmable gate arrays (FPGAs) to create synchronized digital signals that are understandable to communication networks. Our method transforms optical pulses into precisely timed electrical signals that can be analyzed and used in sophisticated network systems. We demonstrated that QNS and dissipation can synchronize a tri-node clock network to the highest precision of thulium atom-based optical lattice clocks. Our work also highlights the practicality of these applications through MATLAB simulations, bridging theoretical principles and real-world solutions with current technology. In our simulations, we utilized an optical signal with a frequency of 263 THz, downconverted to a lower microwave frequency of 100 GHz to achieve subnanosecond-level synchronized signals. The down-converted signal was subjected to white noise and subsequently digitized. The digital signal was then simulated by sampling rate of [Formula: see text] GHz or GSa/s (gigasample per second) and limiting the resolution to [Formula: see text] bits. Finally, high-frequency noise was removed by implementing low-pass filtration using FPGAs. This study takes an essential step toward meeting the rising demands for rapid and efficient data transfer in the ever-evolving digital communications landscape, enabling faster and more reliable connectivity for future communication networks and the quantum Internet.
Tight integration between classical and quantum networking requires strict synchronization of events between the classical and quantum portions of the network. Time-Sensitive Networking (TSN) as defined by IEEE 802.1Q is limited to accuracy on the order of microseconds due to limitations in time synchronization performance; TSN gate control is thus similarly limited. This work presents a new High-Precision TSN that enables greater accuracy and resolution toward sub-nanosecond TSN gate control and can directly support entanglement distribution, a key component in a software-designed quantum network architecture where classical control can reach deep into the quantum network and directly control time critical operations.
The combination of Quantum and Telecommunications networks, offering unparalleled quantum correlation-based capabilities and making it an ideal choice for certain critical applications, requires precise time synchronization across network nodes. This work analytically and experimentally assessed the application of the IEEE 1588 Precision Time Protocol in achieving time synchronization within quantum networks. As results, operating at a repetition rate of 5 MHz, the overall time synchronization precision is 65 ns for single-qubit detection and 100 ns for double-fold coincidence measurements. Correspondingly, the experimental results highlight the role of time-synchronization precision protocols in multi-node quantum networks and also provide insights for further developments for scalable quantum network infrastructure.
Abstract Establishing and maintaining a common time reference across spatially separated devices is a prerequisite for networked quantum experiments and secure communications. Classical two-way timing protocols such as network time protocol or precision time protocol are vulnerable to asymmetric channel delays and cannot provide the picosecond-level precision demanded by quantum repeater networks. We propose and numerically evaluate a quantum-enhanced clock synchronization protocol based on attenuated weak coherent pulses (WCPs) and bidirectional Hong–Ou–Mandel (HOM) interferometry. Our simulations assume telecom-band photons (1550 nm) with a temporal width of 10.0 ns, a repetition rate of f = 10 MHz, effective mean photon number µ = 1.0, detector efficiency η = 85 % , detector timing jitter of 150 ps and channel loss 0.2 dB km −1 . We simulate that sub-nanosecond clock-offset accuracy and precision can be achieved under these operating conditions. This work demonstrates that high-repetition-rate WCPs combined with HOM interference can provide flexible and secure quantum clock synchronization at sub-nanosecond precision.
Precise timing synchronization is essential for distributed quantum networking, enabling entanglement distribution, quantum teleportation, and entanglement swapping across remote nodes. Existing synchronization architectures rely on dedicated timing-distribution infrastructure, most notably White Rabbit networks, which constrain topology, scalability, and deployment in free-space and satellite environments. Here we demonstrate link-free synchronization of quantum network nodes using independently operating miniature rubidium atomic clocks and computational post-processing. We validate the approach on a deployed metropolitan-scale telecom fiber network spanning three geographically separated nodes. Following drift correction, atomic-clock-based synchronization achieves timing performance approaching that of a White Rabbit benchmark and remains stable over continuous 8-hour operation. As a stringent test of quantum-network functionality, we observe Hong-Ou-Mandel interference across spatially separated nodes with visibility exceeding 70%, statistically equivalent to that obtained using dedicated White Rabbit timing links. To the best of our knowledge, this represents the first observation of quantum interference across a deployed metropolitan-scale telecom fiber network synchronized entirely without dedicated timing-transfer infrastructure. These results establish atomic-clock-based synchronization as a scalable, topology-independent alternative to conventional timing-distribution architectures and a practical pathway toward terrestrial, airborne, and space-based quantum networks where dedicated timing links are unavailable.