Information-processing limitations of quantum systems

量子计算机如果实现，将提供前所未有的计算能力，几乎肯定会对我们的社会产生深远的影响。利用这种巨大的信息处理潜力的愿景是量子信息这一令人兴奋的研究领域的驱动力。这一领域的挑战虽然重大，但为物理学和计算机科学的基本问题提供了新的视角。除了可能给我们量子计算机之外，提高我们在控制量子系统方面的技术实力（以及我们对底层物理学的基本理解）可能会以其他目前未预料到的方式造福社会。为了实现这些目标，该计划将评估现有的并提出存储，操纵和传输量子信息的新方法，确定给定量子系统中物理上可能的限制。第一个子项目将开发数值和统计方法，旨在以有效的方式表征复杂的量子系统和过程。这正变得越来越重要，因为实验学家正在迅速扩展他们正在研究的量子基底的剧目。第二个子项目将关注开放量子系统中信息的可靠存储，特别是那些提供某种内在保护的系统。这将有助于纠错和容错计算的理论。此外，该子项目将通过研究光纤电缆的信息承载能力来推进我们对使用量子态的通信的理解。最后，第三个子项目将从不同的角度研究现有的技术和物理信息处理的限制：这些限制往往提供了一个基础的安全密码原语。通过努力根据相应的备选安全假设设计协议，该次级项目将有助于在今后维持可靠的信息安全基础设施。

Quantum computers, if realized, would offer unprecedented computational capabilities and almost certainly have a profound effect on our society. The vision of exploiting this vast information-processing potential is a driving force in the exciting research field of quantum information. The challenges involved in this area, while significant, offer new perspectives on basic questions in physics and computer science. Beyond possibly giving us quantum computers, advancing our technological prowess in controlling quantum systems (as well as our fundamental understanding of the underlying physics) is likely to benefit society in other, currently unanticipated ways. To contribute towards these goals, this program will evaluate existing and propose new ways of storing, manipulating and transmitting quantum information, identifying the limits of what is physically possible in a given quantum system. A first subproject will develop numerical and statistical methods aimed at characterizing complex quantum systems and processes in an efficient manner. This is becoming increasingly relevant as experimentalists are rapidly extending their repertoire of quantum substrates under study. A second subproject will be concerned with the reliable storage of information in open quantum systems, especially those providing a certain type of intrinsic protection. This will contribute to the theory of error-correction and fault-tolerant computing. In addition, this subproject will advance our understanding of communication using quantum states by studying the information-carrying capacity of fiber-optic cables. Finally, a third subproject will examine existing technological and physical information-processing limitations from a different perspective: such restrictions often provide a basis for security of cryptographic primitives. By working towards the design of protocols based on corresponding alternative security assumptions, the subproject will contribute towards maintaining a reliable information security infrastructure into the future.