Experimental Demonstration of Software-Orchestrated Quantum Network Applications over a Campus-Scale Testbed

TL;DR

The paper tackles the challenge of turning laboratory quantum networks into scalable, service-oriented infrastructures. It introduces ArQNet, an SDN-inspired orchestrator built around a three-plane architecture (infrastructure, control, service) to coordinate timing, calibration, and measurement across a campus-scale quantum testbed. The authors demonstrate precise time synchronization (sub-$20$ ps jitter), automated EPS calibration, and automated polarization drift compensation, culminating in a 12-hour continuous entanglement distribution service with high visibilities ($V_{HH}\approx$ 95–100% in various bases) and quantum-state tomography fidelities around $0.83$, across colocated and remote configurations. This work provides a practical path toward programmable, reliable photonic quantum networks and points to future extensions for heterogeneous devices, multi-user access, and fault-tolerant entanglement distribution.

Abstract

To fulfill their promise, quantum networks must transform from isolated testbeds into scalable infrastructures for distributed quantum applications. In this paper, we present a prototype orchestrator for the Argonne Quantum Network (ArQNet) testbed that leverages design principles of software-defined networking (SDN) to automate typical quantum communication experiments across buildings in the Argonne campus connected over deployed, telecom fiber. Our implementation validates a scalable architecture supporting service-level abstraction of quantum networking tasks, distributed time synchronization, and entanglement verification across remote nodes. We present a prototype service of continuous, stable entanglement distribution between remote sites that ran for 12 hours, which defines a promising path towards scalable quantum networks.

Figures (8)

• Figure 1: Architecture of a quantum network using a plane abstraction.
• Figure 2: Dark fiber links between Argonne and partner institutions in the great Chicago area. The inset shows Argonne's quantum network testbed (ArQNet).
• Figure 3: Schematic diagram of the experimental setup for distributing entangled photons and synchronized clock signals across two remote quantum network nodes (Site 2 and Site 3) from a central entangled photon source (Site 1). A multiplexed (MUX 2$\times$1) fiber output carries both clocks (green and red) via radio-over-fiber (RoF) transmission. The fast (10 MHz) and slow (1 PPS) clock signals are combined at Site 1 and distributed over the same optical fiber to both remote sites, where demultiplexers (DEMUX 2$\times$) separate the 10 MHz and 1 PPS clock. The quantum signal is directed via dedicated fiber channels to the remote sites. At each site, the quantum signal is directed to a polarization analyzer (PA), followed by detection via SNSPDs. The clock signals are routed through receivers (RX1, RX2) and detection modules, with Swabian Time Tagger Ultra (TTX) units logging all time-stamped events for synchronized measurement and correlation. The setup supports automated quantum networking experiments including remote two-photon interference and quantum state tomography.
• Figure 4: Improvement in coincidence-to-accidental ratio before (blue) and after (red) EPS optimization (main panel). Inset: correlation of $10$ MHz reference clock pulses at the two remote nodes, confirming precise timing alignment for photon detection.
• Figure 5: EPS calibration versus pump attenuation. Coincidence (C), accidental (A), and coincidence-to-accidental ratio (CAR). The operating point (red marker) corresponds to $0.85\,\mathrm{CAR}_{\max}$, chosen for stability.