# Information Security and Cryptography Research Group

## A de Finetti Representation for Finite Symmetric Quantum States

### Robert Koenig and Renato Renner

Journal of Mathematical Physics, vol. 46, no. 122108, Dec 2005, See also http://arxiv.org/abs/quant-ph/0410229.

Consider a symmetric quantum state on an n-fold product space, that is, the state is invariant under permutations of the n subsystems. We show that, conditioned on the outcomes of an informationally complete measurement applied to a number of subsystems, the state in the remaining subsystems is close to having product form. This immediately generalizes the so-called de Finetti representation to the case of finite symmetric quantum states.

## BibTeX Citation

@article{KoeRen04b,
author       = {Robert Koenig and Renato Renner},
title        = {A de {F}inetti Representation for Finite Symmetric Quantum States},
journal      = {Journal of Mathematical Physics},
number       = 122108,
volume       = 46,
year         = 2005,
month        = 12,