Quantum Internet Architecture

Quantum Internet Architecture

The quantum internet will not replace the classical internet: it will layer on top of it, using classical communication for control plane operations while quantum channels carry entanglement and quantum states. Understanding the layered architecture helps map current experiments to the long-term vision.

The Quantum Internet Alliance Stack

The Quantum Internet Alliance proposes a layered protocol stack analogous to the classical OSI model:

Physical Layer: Quantum channels (fiber, free-space, satellite), photon sources, detectors, quantum memories. Handles physical transmission of qubits and entangled pairs.

Link Layer: Heralded entanglement generation between adjacent nodes. Like classical link layer, handles single-hop communication. Provides "Bell pair delivery" as a service to the network layer.

Network Layer: Entanglement swapping across multiple hops. Routes entanglement from source to destination through intermediate nodes. Analogous to IP routing but for quantum resources.

Transport Layer: Entanglement distillation (purification) and error management. Ensures the entanglement delivered to the application layer meets quality (fidelity) requirements.

Application Layer: QKD, blind quantum computing, clock synchronization, distributed sensing. Applications that consume Bell pairs or quantum states.

Control Plane vs Data Plane

Like classical networks, the quantum internet separates control and data:

Control plane (classical): Orchestrates resource allocation, routing decisions, heralding signals, error correction messages, classical post-processing. Runs on classical computers at each node.

Data plane (quantum): The actual quantum state transmission, entanglement generation, and qubit storage. Operates according to instructions from the control plane.

The key difference from classical networks: quantum data plane operations are probabilistic (entanglement generation may fail), so the control plane must handle high rates of retransmission and re-routing.

Node Types

End nodes: Alice and Bob. Require a quantum transceiver (can generate or detect photons) and optionally quantum memory for synchronization.

Repeater nodes: Intermediate nodes with quantum memory, two-photon Bell state measurement capability, and sufficient coherence to wait for neighboring segment entanglement.