2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/91165We demonstrate single-photon interference over 100 km using a balanced gated-mode photon detector and a plug & play system for quantum key distribution. The visibility with 0.1 photon/pulse was more than 80% after 100 km transmission. This corresponds to the fidelity of a quantum cryptography system of more than 90% and a QBER of less than 10%, satisfying the security criteria.Submitted to Electronics Letters on May 16, 2003Quantum Physicstext