Implications of Disentanglement and Locality Induction for Quantum Information Processing and Cryptography

摘要

Entanglement and non-locality are global properties that depend on the coherence of quantum system states that allow one to carry out communications and information processing tasks often more efficiently than using only systems in classical physical states. However, environmental noise and loss, even locally, can threaten these quantum properties. This typically occurs asymptotically, in decay-like manner. Nonetheless, sudden death of these properties can also take place in the form either of entanglement sudden death (ESD) or of Bell non-locality sudden death (BNSD), defined as the falling of the corresponding entanglement-related parameter to zero in finite time from an earlier non-zero value. Moreover, such sudden death processes can occur while state coherence itself still remains non-zero. Here, such possible threats to quantum information processing and cryptography are discussed, via examples from both discrete and continous variable properties, including the use of strong entanglement witnesses in the demonstration of ESD.