Describe the role of quantum repeaters in extending the range of Quantum Key Distribution (QKD) networks.

Quantum repeaters play a crucial role in extending the range of Quantum Key Distribution (QKD) networks, which are essential for secure quantum communication over long distances. To understand their role, let's delve into the challenges QKD faces in terms of transmission range and how quantum repeaters address these challenges. Challenges in Long-Distance Quantum Communication: Quantum communication systems, including QKD, are based on the principles of quantum mechanics, which allow for the secure exchange of cryptographic keys. However, these systems face significant challenges when it comes to long-distance transmission: 1. Quantum Signal Loss: As quantum signals propagate through optical fibers, they experience signal loss due to factors such as fiber attenuation and scattering. This limits the distance over which quantum signals can be reliably transmitted. 2. Quantum Noise and Decoherence: Quantum signals are sensitive to environmental factors and can be subject to noise and decoherence, which can disrupt the delicate quantum states of photons. 3. Quantum State Degradation: Over long distances, the quality of quantum states can degrade ....