Argonne Quantum Network (ArQNet) Orchestrator Achieves 12 Hours of Continuous, Stable Entanglement Over Deployed Campus Fiber
A research team led by scientists from Northwestern University and Argonne National Laboratory (ANL) has announced a major accomplishment that advances the field of quantum networking. For the Argonne Quantum Network (ArQNet) testbed, the team successfully created and showed a prototype orchestrator that automates and controls intricate quantum communication experiments using concepts from software-defined networking (SDN).
This innovation establishes a scalable architecture that can verify entanglement between distant nodes, provide distributed time synchronization, and abstract quantum networking operations at the service level. Importantly, the researchers were able to run a prototype service that sustained a steady, continuous distribution of entanglement across stations for 12 hours. Basic quantum communication experiments are transformed into dependable quantum networking services in this demonstration.
You can also read Technology Prosperity Deals Unite U.S., Japan, and Korea
Bridging the Gap: From Testbed to Infrastructure
To realise their potential, quantum networks which hold promise for uses such as distributed quantum computation, ultra-secure communication, and quantum-enhanced metrology must evolve from standalone physics experiments into reliable, scalable infrastructure. Because quantum information depends on probabilistic entanglement production, requires extremely accurate time synchronization, and decoheres quickly owing to ambient noise, coordinating network functions using fragile quantum states poses previously unheard-of difficulties.
By offering a single control framework for integrating many physical subsystems, the ArQNet orchestrator overcomes these basic limitations. It uses the same three-plane abstraction approach as traditional SDN:
- The Infrastructure Plane: This plane consists of the quantum network’s actual hardware, including all-optical switches, polarization analyzers (PAs), time taggers (TTUs), entangled-photon sources (EPS), and the fibre links that connect the devices.
- The Control Plane: This layer controls core network operations and is implemented as a centralized orchestrator. While scheduling, resource management, and topology management are handled similarly to classical networks, entanglement management a non-classical network function is crucially included. The infrastructure plane receives exact instructions from the orchestrator to carry out timing and calibration procedures.
- The Service Plane: This plane provides customers or applications with end-to-end services like entanglement distribution or quantum teleportation. The entanglement distribution service was the main focus of the ArQNet work.
The ArQNet testbed, a campus-to-metro scale platform with five locations connected in a partial mesh topology via deployed dark fibre lines, served as the platform for the implementation.
You can also read Quantum New Special Purpose Acquisition Company Canada
Achieving Picosecond Synchronization and Stability
Accurate synchronization is essential for dependable entanglement distribution; timing drift at the millisecond level can destroy quantum interference and compromise distributed protocols. By combining a 10 MHz clock for frequency locking, a 1 PPS (pulse-per-second) signal for absolute alignment, and Network Time Protocol (NTP) for protocol coordination, the ArQNet system established a hybrid synchronization architecture across many sites. Using radio-over-fiber (RoF) clock delivery, these timing signals were co-distributed over dedicated fibre.
With an RMS jitter of 12.19 ps at the remote nodes, measurement results verified a very steady clock distribution, which is necessary for accurate coincidence measurements.
The orchestrator does more than only time; it also automates crucial calibration operations that are required for ongoing operation.
- EPS Calibration: To maximize the coincidence-to-accidental ratio (CAR), the system automatically adjusts the Entangled Photon Source’s (EPS) pump attenuation. To provide stability over long runs, an operating point of 0.85×CARmax was used.
- Polarization Drift Compensation: The entanglement quality is deteriorated by polarization drift, which is caused by environmental conditions in deployed fibre. An automated polarization compensation procedure built into the orchestrator allows for remote, self-adjusting readjustment. Polarization analyzers (PAs) with four variable wave plates at distant nodes are used in this procedure. In order to transform a physical-layer instability into a control-layer solution, the system iteratively modifies these plates to minimise measured photon counts for particular polarization states.
You can also read MDI-CV Protocol Redefining Quantum Network Verification
Validation of Remote, High-Fidelity Entanglement
Two-Photon Interference (TPI) and Quantum State Tomography (QST), two complex quantum experiments, were carried out in both co-located and entirely remote setups to verify the orchestrator’s capabilities. High-quality interference was measured in the fully remote configuration, with detectors at Sites 2 and 3 (about 3.19 km and 5.28 km from the source, respectively) separated by installed fibre.
The QST for the totally remote configuration produced a high fidelity (F) of roughly 83.3% with the target Bell state ∣Φ +⟩, despite the difficulties caused by two asymmetric links that were suffering uncorrelated noise. For the remote scenario, the computed concurrence was C=0.704, which suggests a high level of entanglement.
Importantly, the orchestrator’s automation significantly decreased operational overhead, needing only one user rather than several operators coordinating across sites, and reducing the average experiment run time from more than a day to roughly 1.5 hours.
The 12-Hour Autonomy Milestone
Demonstrating the prototype service for continuous, stable entanglement dissemination was the main accomplishment. Over the course of 12 hours, this service constantly coordinates TPI measurements. The average fringe visibility (V) is continuously monitored by the system. An automated realignment process is initiated by the orchestrator whenever V drops below a certain threshold (V th).
Over the course of its 12-hour autonomous run, the experiment was able to sustain visibility above the necessary threshold. This demonstrates that the ArQNet orchestrator can enable the autonomous operation and high availability required for production-grade quantum networks.
The U.S. Department of Energy (DOE)-sponsored study lays a strong foundation for programmable, service-oriented photonic quantum networks. ArQNet successfully closes the large gap between laboratory quantum optics and scalable quantum internet infrastructures by combining accurate synchronization with modular orchestration.
You can also read TF-QKD Twin-Field Quantum Key Distribution Over 830-km Fibre
