Category: The Completeness of Quantum Physics

Bell derived his inequality in 1965, believing that an actual experimental test was still a long way off. But in 1972, John Clauser at the University of California, Berkeley figured out a nifty way to test it (though using paired photons instead of electrons). The result was that Bell’s inequality was violated, indicating that nature…

Preoccupied by the lead-up and aftermath of the Second World War, physicists temporarily set aside further attempts to figure out the more esoteric implications of quantum physics. The next big step had to wait for the Irish physicist John Bell to take a sabbatical year in 1964. Bell had long been interested in the strangeness…

The only way to preserve the ultimate speed limit of special relativity in the EPR scenario was to say that the spin state of each individual electron must have actually existed before the measurement, even if there was no way to know what it was. In other words, there must be some “hidden variable” that…

But wait, something even stranger is going on here. Given the geometry that we have assumed (which is perfectly acceptable by the laws of physics) the “influence” has to travel from A to B much faster than the speed of light. Since the theory of special relativity tells us that no matter or energy could possibly travel faster than…

In 1935, after a lull in the long-running debate between Bohr and Einstein, the latter genius stunned the physics community with another important Gedankenexperiment. Even though Bohr had successfully refuted all of his arguments to date, Einstein was not quite ready to accept the Copenhagen interpretation. He still wasn’t happy with the inherent uncertainty in…

We will continue to dig deeper into the basic question of what quantum physics actually means. We have become familiar with many ways in which this theory challenges traditional understandings of science, reality, and even common sense. Now we will look at some of the ways quantum physics responds to these challenges. Along the way,…