Syndrome-as-Header: A Quantum Label-Switching Architecture via Uncorrectable Error Injection

Scaling quantum networks beyond simple point-to-point links requires efficient packet-switching mechanisms. Traditional approaches, such as Optical Burst Switching (OBS) or quantum-wrapper-based switching, rely on external classical headers that must be precisely synchronized with the quantum payload. This requirement creates significant bottlenecks due to control-plane timing uncertainty, guard-window failures, and the need for complex fiber delay lines. This paper investigates whether routing information can be embedded directly into the quantum payload itself to bypass these timing constraints.

The authors propose Syndrome-as-Header (SAH), a label-switching architecture that utilizes the syndrome structure of quantum error correction codes (QECCs). By employing Uncorrectable Error Injection (UEI), the researchers map flow labels to specific reference syndromes. These reference syndromes are chosen to be distinct from the syndromes generated by standard channel noise, ensuring that routers can identify the header while simultaneously suppressing correctable channel errors. The architecture supports two modes: FAST forwarding for autonomous switching and VERIFICATION for end-to-end consistency checking. Crucially, routers perform these operations—label extraction, error correction, and label swapping—without ever measuring or decoding the underlying logical quantum state.

SAH effectively decouples the forwarding process from the strict timing alignment required by external classical headers. In simulations using NSFNet benchmarks, SAH maintains higher throughput and packet acceptance rates than traditional OBS and quantum-wrapper baselines under high-jitter conditions. Because the forwarding information is embedded in the syndrome domain, the timing uncertainty of the control plane is transformed into a manageable memory-residence penalty rather than a fatal alignment-budget failure. The protocol allows for autonomous, hop-by-hop label swapping, making it a robust candidate for scalable, QEC-enabled quantum networks.