Mr. Vipul Kumar Bondugula

Quantum Repeater Architectures for Reliable Long Distance Quantum Cryptography

Abstract:

Quantum cryptography provides exceptional security by utilizing the fundamentals of quantum mechanics. One major obstacle in its application is the loss of photons over extended distances in fiber optics and free-space communication channels. Photon attenuation and scattering weaken the quantum signals, increasing the likelihood of transmission errors. This challenge limits the practicality of deploying large-scale quantum networks. To overcome this, quantum repeaters have been developed as intermediate nodes that expand communication distances while preserving quantum coherence. They divide the communication link into smaller segments that share entangled photon pairs. These segments are connected through entanglement swapping and purification methods, effectively restoring quantum correlations over long distances. Unlike classical repeaters, quantum repeaters maintain the integrity of quantum states without copying or measuring them, preserving the security of quantum key distribution. The introduction of quantum repeaters significantly decreases photon loss, enabling secure communication over hundreds or thousands of kilometers. By sustaining entanglement across vast distances, quantum repeaters move theoretical quantum communication closer to practical, scalable networks. Current research focuses on optimizing the design of these repeaters, reducing errors, and improving entanglement fidelity. These developments are essential for the future realization of a global quantum internet. Quantum repeaters represent a crucial advancement in addressing photon loss and supporting secure long-distance quantum communication.