Small:CIF:Exact Thresholds for Quantum Information Processing

University Of California-Santa Barbara, Santa Barbara CA

Investigators

Abstract

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.