



01374nas a2200133   4500008004100000245008300041210006900124260001500193520094600208100001401154700001801168700001701186856003701203       2010                        eng d00aOptimal Perfect Distinguishability between Unitaries and Quantum  Operations
0 aOptimal Perfect Distinguishability between Unitaries and Quantum  c2010/10/123 a  We study optimal perfect distinguishability between a unitary and a general
quantum operation. In 2-dimensional case we provide a simple sufficient and
necessary condition for sequential perfect distinguishability and an analytical
formula of optimal query time. We extend the sequential condition to general
d-dimensional case. Meanwhile, we provide an upper bound and a lower bound for
optimal sequential query time. In the process a new iterative method is given,
the most notable innovation of which is its independence to auxiliary systems
or entanglement. Following the idea, we further obtain an upper bound and a
lower bound of (entanglement-assisted) q-maximal fidelities between a unitary
and a quantum operation. Thus by the recursion in [1] an upper bound and a
lower bound for optimal general perfect discrimination are achieved. Finally
our lower bound result can be extended to the case of arbitrary two quantum
operations.
1 aLu, Cheng1 aChen, Jianxin1 aDuan, Runyao  uhttp://arxiv.org/abs/1010.2298v1