Lets suppose device A measures the position of a particle very accurately. Device B now cannot measure its momentum to high accuracy due to the uncertainty principle. But lets suppose that neither A nor B can ever communicate their findings to the rest of the world. Now the uncertainty principle can be violated because no observer can ever put the two pieces of information together and know more about the state of the particle than is usually allowed. So how does one devise an experiment such that a scientist knows that device A measured a particle's position very accurately and that device B measured its momentum very accurately but without being able to know the actual values recorded by both.