As quantum computing approaches practical realization, current cryptographic systems face unprecedented vulnerabilities requiring quantum-resistant security solutions. This research investigates quantum key distribution (QKD) protocols and post-quantum cryptographic algorithms for securing digital communications. We implemented BB84 and E91 QKD protocols using polarized photons and achieved key distribution rates of 1.2 Mbps over 50km fiber optic networks with 10^-11 quantum bit error rates. Comparative analysis of lattice-based, code-based, and multivariate cryptographic systems reveals optimal combinations for different security requirements. The study provides practical guidance for transitioning to quantum-safe cryptography and maintaining information security in the quantum era.