document: Non-optimal universal quantum deleting machine We verify the non-existence of some standard universal quantum deleting machine . Then a non-optimal universal quantum deleting machine is constructed and we emphasize the difficulty for improving its fidelity . In a way , our results complement the universal quantum cloning machine established by Buzek and Hillery -LRB- 1996 -RRB- , and manifest some of their distinctions
doc_bio_tags: B I I I I O O O O O O O O O O O O O O B I I I I O O O O O O O O O O B O O O O O O O O O B I I I O O O O O O O O O O O O O O O
extractive_keyphrases: nonoptimal universal quantum deleting machine fidelity universal quantum cloning machine
abstractive_keyphrases: nuqdm