Small:CIF:Exact Thresholds for Quantum Information Processing

计算和通信是物理过程，受到物理定律的限制。该项目研究量子力学定律对以可靠的方式处理量子信息的限制。具体解决了两个问题，一个是关于量子计算机中可以容忍的噪声量，另一个是关于存储量子信息所需的最小物理资源。噪声抑制：当谈论实现量子算法的电路时，人们必须考虑到这样一个事实，即不可能完美地实现门。在量子计算的情况下，这种实现是特别相关的，因为实现量子门的实验挑战明显大于实现经典门的挑战。 容错量子计算理论研究了这个问题的许多方面。目前的项目研究的是在什么样的噪声水平下，量子计算的能力会消失，以及这种阈值如何取决于量子门的类型和噪声的类型。信息存储：显然，要存储一点信息，需要消耗物理资源，而这些资源（如空间和能量）之间存在权衡。该项目的研究着眼于通过推导物理定律来使这种直觉更加严格和定量，这些物理定律给出了可靠存储量子信息所需的组合资源的确切下限，同时考虑到必须存储多少信息多长时间。

Computation and communication are physical processes with limits set by the laws of physics. This project investigates which bounds the laws of quantum mechanics impose on processing quantum information in a reliable manner. Two questions are specifically addressed, one concerning the amount of noise that can be tolerated in a quantum computer, and the other about the minimal physical resources required to store quantum information. Noise Thresholds: When talking about circuits to implement quantum algorithms one has to take into account the fact that it is impossible to implement the gates perfectly. In the case of quantum computation this realization is especially relevant as the experimental challenges for implementing quantum gates are significantly greater than those for implementing classical gates. It is the theory of fault tolerant quantum computation that investigates the many aspects of this issue. The current project looks at exactly which noise levels the ability to perform quantum computation disappears and how such threshold values depend on the kind of quantum gate and the kind of noise.Information Storage: It seems obvious that to store a bit of information one needs to expend physical resources and that there is a trade-off between these resources such as space and energy. The research of this project looks at making this intuition rigorous and more quantitative by deriving physical laws that give exact lower bounds on the necessary combined resources to store quantum information reliably, taking into account how much information for how long has to be stored.