Experimental Proof of Quantum Nonlocality without Squeezing

Abstract

It is shown that the ensemble $\{p (α),|α>|α^*>\}$ where $p (α)$ is a Gaussian distribution of finite variance and $| α>$ is a coherent state can be better discriminated with an entangled measurement than with any local strategy supplemented by classical communication. Although this ensemble consists of products of quasi-classical states, it exhibits some quantum nonlocality. This remarkable effect is demonstrated experimentally by implementing the optimal local strategy together with a joint nonlocal strategy that yields a higher fidelity.