论文标题
将量子容量与标记的扩展界限
Bounding the quantum capacity with flagged extensions
论文作者
论文摘要
在本文中，我们考虑了量子通道的凸组合的标记扩展，并为标记扩展的降解性找到了足够的条件。即时应用是对任何频道的量子$ Q $和私人$ p $的限制，是统一地图和另一个频道的混合物，与单一组件大于$ 1/2 $相关的概率。然后，我们将足够的条件专门用于标记的Pauli频道，在Pauli频道的量子和私人能力上获得了上限的家庭。特别是，我们在去极化通道，BB84通道和广义振幅阻尼通道的量子和私有能力上建立了新的最新上限。此外，标记的结构可以自然地应用于限制性降解条件下的通道的张量功能，这表明可以通过考虑大量的通道使用来找到更好的上限。
In this article we consider flagged extensions of convex combination of quantum channels, and find general sufficient conditions for the degradability of the flagged extension. An immediate application is a bound on the quantum $Q$ and private $P$ capacities of any channel being a mixture of a unitary map and another channel, with the probability associated to the unitary component being larger than $1/2$. We then specialize our sufficient conditions to flagged Pauli channels, obtaining a family of upper bounds on quantum and private capacities of Pauli channels. In particular, we establish new state-of-the-art upper bounds on the quantum and private capacities of the depolarizing channel, BB84 channel and generalized amplitude damping channel. Moreover, the flagged construction can be naturally applied to tensor powers of channels with less restricting degradability conditions, suggesting that better upper bounds could be found by considering a larger number of channel uses.
