Just about anyone who has worked with quantum mechanics will agree that it is weird. One of the reasons for this consensus is that it is very counterintuitive compared to the classical mechanics that dominate the world around us. Researchers at the University of Vienna and many other institutions have recently taken a major step towards confirming that quantum mechanics is not only counterintuitive but contradicts classic mechanics.
Entanglement is one of the more fundamental phenomena of quantum mechanics as it demonstrates how the states of particles can be made dependent on each other. This is where the contradiction can exist, if two entangled particles have their states measured while being too far away for the information of one particle's state to reach the other. Experiments have been created to test if indeed entanglement is a purely quantum mechanical phenomenon or if some classical process can explain it, but none have been strict enough to settle the question until now. The researchers' new experiment is able to capture every single entangled photon created, thereby leaving no doubt of what happens.
While the implications to how quantum and classical mechanics interact are the most obvious results of this experiment and those to come, this could lead to improved quantum cryptography. In theory quantum cryptography is secured against eavesdropping, but that protection is only perfect if entanglement is a purely quantum phenomenon, and so far, that appears to be the case.
Source: University of Vienna