Measurement-Device-Independent Quantum Private Query With Weak Coherent Source

Quantum private query (QPQ) has emerged as a pivotal quantum cryptographic solution for symmetric private information retrieval, representing one of the most viable protocols for practical implementation following quantum key distribution. However, comprehensive practical security analysis remains imperative before deployment, particularly addressing concurrent vulnerabilities at both the optical source and detection components. This study makes dual fundamental contributions: 1) We unveil a sophisticated multiphoton attack strategy that enables malicious users to completely compromise database confidentiality by exploiting inherent multiphoton emissions from practical light sources across multiple established QPQ protocols; 2) We develop a novel decoy-state measurement-device-independent QPQ protocol specifically designed for weak coherent sources that simultaneously mitigates security vulnerabilities at both system endpoints. Our rigorous security analysis demonstrates that the proposed protocol achieves remarkable security enhancement - reducing an attacker’s information extraction capability from complete database access (100% items) to merely approximately 2.51 database items under standard operational parameters, while preserving practical implementability. This work establishes a critical framework for bridging theoretical security guarantees with practical implementation requirements, providing essential foundations for real-world QPQ deployment within existing quantum communication infrastructures.