Entanglement without Classical Correlations

Quantum mechanics is full of counterintuitive concepts. The idea of entanglement – when two or more particles instantaneously exhibit dependent characteristics when measured, no matter how far apart they are – is one of them. Now, physicists have discovered another counterintuitive result that deals with the line between the quantum and classical worlds.

Normally, when two or more particles are entangled (and seem to communicate with each other instantaneously), they not only share quantum correlations, but also classical correlations. Although physicists don’t have an exact definition for classical correlations, the term generally refers to local correlations, where information does not have to travel faster than the speed of light.

But a team of physicists from the National University of Singapore, Mediterranean Technology Park in Barcelona, the University of Leeds, and the University of Bristol has demonstrated something different. They’ve theoretically shown that any odd number (greater than one) of entangled particles can exist without classical correlations. They explain this paradox in a recent issue of Physical Review Letters.

“One way of seeing this is as follows,” Vlatko Vedral, Professor of Quantum Information Science at the University of Leeds, told PhysOrg.com. “Entanglement means being correlated as far as many different measurements are concerned. Classical correlations mean being correlated as far as one particular measurement is concerned. That is why researchers usually think that when there is entanglement, there are also classical correlations. However, our paper shows that you have to be careful about making this inference.”

Source: http://www.physorg.com/news139051854.html