//! Photon pair sources and quantum entanglement module.
//!
//! Provides:
//! - SPDC (Spontaneous Parametric Down-Conversion) photon pair sources
//! - Quantum entanglement measures (concurrence, negativity, von Neumann entropy)
//! - Bell inequality tests (CHSH, CH, Mermin)
//! - Quantum Key Distribution protocols (BB84, E91, CV-QKD)
pub use *;
pub use *;
pub use *;
pub use *;