High-Dimensional Quantum Cloning and Applications to Quantum Hacking

Attempts at cloning a quantum system result in the introduction of imperfections in the state of the copies. This is a consequence of the no-cloning theorem, which is a fundamental law of quantum physics and the backbone of security for quantum communications. Although perfect copies are prohibited, a quantum state may be copied with maximal accuracy via various optimal cloning schemes.

http://advances.sciencemag.org/content/3/2/e1601915.full