One-sided device-independent quantum secure direct communication with single-photon sources

Abstract

Quantum secure direct communication (QSDC) enables the direct transmission of confidential messages without pre-establishing a secret key. Device independence (DI) can further enhance its practical security against untrusted devices. However, existing DI-QSDC protocols rely on a single Clauser–Horne–Shimony–Holt inequality, which severely limits both the achievable communication distance and the secret message capacity, while the detection loophole remains open in DI-QSDC. To overcome these limitations, we propose a one-sided DI-QSDC protocol based on single-photon sources and heralded entanglement. The protocol combines entanglement distribution, loss-tolerant steering-based security verification, and measurement-DI communication verification and decoding. We employ the Navascués–Pironio–Acín hierarchy based semidefinite programming relaxations to evaluate the secret message capacity. Numerical simulations show that our protocol extends communication distances by factors of 5.6 and 32.2, and improves the practical secure communication efficiency by factors of 1.8 and 1102.5, compared to single-photon-source-based DI-QSDC and SPDC-based DI-QSDC, respectively.