MIT researchers have proposed an experiment that may close the last major loophole of physicist John Bell's inequality-a 50-year-old theorem that, if violated by experiments, would mean that our universe is based on the less-tangible probabilities of quantum mechanics.
In 1964, Bell took on this seeming disparity between classical physics and quantum mechanics, stating that if the universe is based on classical physics, the measurement of one entangled particle should not affect the measurement of the other-a theory, known as locality, in which there is a limit to how correlated two particles can be.
The loophole that is left proposes that a particle detector's settings may "conspire" with events in the shared causal past of the detectors themselves to determine which properties of the particle to measure-a scenario that, however far-fetched, implies that a physicist running the experiment does not have complete free will in choosing each detector's setting.
MIT's David Kaiser, the Germeshausen Professor of the History of Science and senior lecturer in the Department of Physics, along with MIT postdoc Andrew Friedman and Jason Gallicchio of the University of Chicago, have proposed an experiment, that if two quasars on opposite sides of the sky are sufficiently distant from each other, they would have been out of causal contact since the Big Bang some 14 billion years ago, with no possible means of any third party communicating with both of them since the beginning of the universe - an ideal scenario for determining each particle detector's settings.
Kaiser said that the experiment would go something like this: A laboratory setup would consist of a particle generator, such as a radioactive atom that spits out pairs of entangled particles. One detector measures a property of particle A, while another detector does the same for particle B. A split second after the particles are generated, but just before the detectors are set, scientists would use telescopic observations of distant quasars to determine which properties each detector will measure of a respective particle. In other words, quasar A determines the settings to detect particle A, and quasar B sets the detector for particle B.
The paper has been published in the journal Physical Review Letters.
