Polar wiretap coding for practical quantum confidentiality

We present a quantum-assisted protocol that provides a confidential data channel under the assumption of pre-shared keys. The pre-shared key can be reused across multiple sessions, reducing the cost of fresh key generation. The protocol does not require an authenticated classical feedback channel during execution. Confidentiality is ensured by the physical properties of quantum states and information-theoretic preprocessing using polar codes within the Wyner wiretap framework. The construction avoids entanglement and quantum memories, enabling deployment with current hardware. Due to the physics of quantum communication, the protocol is point-to-point with limited throughput, but is suitable for high-assurance, moderate-rate applications.