标题： 量子Doeblin系数：收缩系数的简单上界 显示英文标题

标题： Quantum Doeblin coefficients: A simple upper bound on contraction coefficients

摘要： 收缩系数为数据处理不等式提供了定量的加强。 因此，当需要对信息处理进行更深入的分析时，它们有许多自然的应用。 然而，计算这些系数通常具有挑战性。 作为补救措施，我们讨论了Doeblin系数的量子推广。 这些系数给出了许多收缩系数的有效计算上界。 我们证明了几个性质，并讨论了推广和应用。 特别是，我们给出了额外的更强的界限。 一个特别适用于PPT通道，另一个则基于约束松弛适用于一般通道。 此外，我们引入了反向Doeblin系数，它们可以限制某些扩展系数。 显示英文摘要

摘要： Contraction coefficients give a quantitative strengthening of the data processing inequality. As such, they have many natural applications whenever closer analysis of information processing is required. However, it is often challenging to calculate these coefficients. As a remedy we discuss a quantum generalization of Doeblin coefficients. These give an efficiently computable upper bound on many contraction coefficients. We prove several properties and discuss generalizations and applications. In particular, we give additional stronger bounds. One especially for PPT channels and one for general channels based on a constraint relaxation. Additionally, we introduce reverse Doeblin coefficients that bound certain expansion coefficients.