Author: Haroon Khalil
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Quantum Logic
Many of the problems we run across in trying to understand quantum physics are apparent conflicts with standard logic. To avoid the need to go too deeply into formal logic, we have usually presented arguments that appeal to common sense (based on our experience with the everyday world). The rules of formal logic are abstract,…
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The Holographic Universe
Yet another way to deal with the puzzling aspects of quantum physics is to completely redefine objective reality. After all, everything we know about the world must be filtered through our various senses. And we know of many cases where our senses can be fooled, such as optical illusions. Maybe our entire image of the…
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The de Broglie-Bohm Interpretation
Despite the triumph of Bell’s theorem, there have been a few serious attempts to apply the concept of hidden variables to get around the apparent lack of objective (observer-independent) reality at the quantum level. Interpretations of this type retain both objective reality and determinism, by postulating a real physical quantity or “force” that we have…
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The Many Worlds Interpretation
We’ll begin with a completely different way of dealing with the measurement problem. As you’ll recall, the conventional interpretation of quantum physics says that something dramatic happens to wave functions when a measurement occurs. Let’s consider the simple case of a single quantum particle. Before a measurement, its wave function may be spread over a…
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Introduction
Trying to figure out the true meaning of quantum physics and the nature of reality is a tall order. Although a lot has been written and said on the subject in the last few decades, it’s worth noting that many practicing physicists would say most of this discussion is well outside the realm of physics.…
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The Aspect Experiment
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…
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Bell’s Inequality
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…
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Hidden Variables
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…
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Spooky Action at a Distance
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…
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The EPR Paradox
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…