Abstract
The quantum versions of de Finetti’s theorem derived so far express the convergence of -partite symmetric states, i.e., states that are invariant under permutations of their parties, toward probabilistic mixtures of independent and identically distributed (IID) states of the form . Unfortunately, these theorems only hold in finite-dimensional Hilbert spaces, and their direct generalization to infinite-dimensional Hilbert spaces is known to fail. Here, we address this problem by considering invariance under orthogonal transformations in phase space instead of permutations in state space, which leads to a quantum de Finetti theorem particularly relevant to continuous-variable systems. Specifically, an -mode bosonic state that is invariant with respect to this continuous symmetry in phase space is proven to converge toward a probabilistic mixture of IID Gaussian states (actually, identical thermal states).
- Received 30 April 2009
DOI:https://doi.org/10.1103/PhysRevA.80.010102
©2009 American Physical Society