Practical challenges in quantum key distribution
  Quantum key distribution (QKD) promises unconditional security in data communication and is currently being deployed in commercial applications. Nonetheless, before QKD can be widely adopted, it faces a number of important challenges such as secret key rate, distance, size, cost and practical security. Here, we survey those key challenges and the approaches that are currently being taken to address them. 
Eleni Diamanti, Hoi-Kwong Lo, Bing Qi and Zhiliang Yuan
quant-ph