Institute for Quantum Information (IQI) Weekly Seminar

**NOTE ROOM CHANGE**

When analysing quantum information processing protocols one has to deal
with large entangled systems, each consisting of many subsystems. It is therefore necessary to find some additional structure of the relevant state space, which can allow us to simplify the analysis. de Finetti theorems enable a substantially simplified analysis of information-processing tasks by giving us a way to relate states, which are symmetric under permutation of the subsystems, to states in which the subsystems are independent of each other. This relation plays an important role in various areas, e.g., in quantum cryptography or state tomography, where permutation invariant systems are ubiquitous. The known de Finetti theorems usually refer to the internal quantum state of a system and depend on its dimension. In this talk a different de Finetti theorem will be presented, where systems are modelled in terms of their statistics under measurements. This is necessary for a large class of applications widely considered today, such as device independent protocols, where the underlying systems and the dimensions are unknown. 
In the talk I will explain the concept of de Finetti theorems, motivate the need for a device independent de Finetti theorem and present the new results.

Joint work with Renato Renner
Reference: http://arxiv.org/abs/1308.0312