Error Management

Different from qubit-based quantum computing, optical quantum communication relies on bosonic modes to generate entangled states for long-distance transmission, without the need for universal gate sets. Thus, we require methods that can tolerate photon loss, imperfect entanglement generation, and heterogeneous device noise, while remaining practical for near-term testbeds and scalable to future large networks. InterQnet adopts a layered approach to error management: (1) lightweight error detection via Pauli Check Sandwiching (PCS) and post-selection, (2) resource-aware strategies that leverage gauge freedom to simplify correction, (3) entanglement distillation protocols that convert multiple noisy Bell pairs into fewer high-fidelity ones, and (4) advanced quantum LDPC (qLDPC) and bosonic codes that enable scalable, fault-tolerant entanglement purification. Together, these techniques form a hierarchy that links the device-level realities of Thrust 1 to the architectural protocols of Thrust 3, and they map naturally onto the two project goals: enabling practical demonstrations in InterQnet-Achieve and guiding at-scale design choices in InterQnet-Scale.

(a) Quantum error detection for novel entanglement distillation protocol that can distill two Bell pairs from four imperfect ones. (b) Quantum error correction with concatenated bosonic GKP code and qLDPC code. (c) Efficient and robust purification of logical Bell pairs with qLDPC codes.