Is there a universal quantum machine to examine the precision of unknown quantum states
Shengshi Pang, Shengjun Wu, Zeng‐Bing Chen · arXiv (Cornell University) · 2011
In this work, we reveal a new type of impossibility discovered in our recent research which forbids comparing the closeness of multiple unknown quantum states with any non-trivial threshold in a perfect or an unambiguous way. This impossibility is distinct from the existing impossibilities in that it is a collective impossibility on multiple quantum states while most other no-go theorems concern with only one single state each time, i.e., it is an impossibility on a non-local quantum operation. This novel impossibility may provide a new insight into the nature of quantum mechanics and it implies more limitations on quantum information tasks than the existing no-go theorems.