Quantum repeater

A quantum repeater is a system designed to overcome the challenge of transmitting quantum information over long distances in fiber-optic networks, where photon loss is significant. Unlike classical repeaters, which amplify signals, quantum repeaters rely on a sequence of entanglement links to extend the communication range without violating the no-cloning theorem, which prohibits copying quantum information. Quantum repeaters function by dividing the transmission distance into smaller segments. They use entangled photons and quantum memories to store and manage entanglement across these segments. Through processes like Bell State Measurements (BSMs), the entanglement is extended step by step until it connects distant parties. Key technologies for quantum repeaters include high-performance quantum memories, capable of storing and retrieving entangled photons efficiently, and frequency-conversion interfaces that adapt photons to telecom wavelengths for fiber-optic compatibility.