Experimental Proof of Quantum Nonlocality without Squeezing

It is shown that the ensemble ${p (alpha),|alpha>|alpha^*>}$ where $p (alpha)$ is a Gaussian distribution of finite variance and $| alpha>$ 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.