Nonlocal correlations are generic in infinite-dimensional bipartite systems

It was recently shown that nonseparable density operators on the Hilbert space ${\mathcal{H}}_1\otimes {\mathcal{H}}_2$ are trace norm dense if either factor space has infinite dimension. We show here that nonlocal states, i.e., states whose correlations cannot be reproduced by any local hidden variable model, are also dense. Our constructions distinguish between the case $\dim {\mathcal{H}}_1=\dim {\mathcal{H}}_2=\infty ,$ where we show that states violating the Clauser-Horne-Shimony-Holt (CHSH) inequality are dense, and the case $\dim {\mathcal{H}}_1<\dim {\mathcal{H}}_2=\infty ,$ where we identify open neighborhoods of nonseparable states that do not violate the CHSH inequality but show that states with a subtler form of nonlocality (often called “hidden” nonlocality) remain dense.