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Quantum Wierdness

There are three features of quantum theory that make it extremely counterintuitive.  However, a little reflection reveals that two of these features could not have been otherwise, and the third is wrong.

Table of Contents

Quantum Wierdness
Niels Bohr, one of the founding fathers of quantum theory, once said that “Anyone who is not shocked by quantum theory has not understood it.1”  Indeed, quantum theory causes almost universal uneasiness because it is the most accurate theory ever invented2, yet is widely criticized as making no intuitive sense.  The cause of the difficulty in understanding the theory seems to stem from three strange predictions it makes that are in their own right difficult to accept, as follows:

  1. Indeterminism
  2. Nonlocality
  3. The role of consciousness in observation.

I will argue that indeterminism is philosophically necessary, nonlocality is logically implied by indeterminism, and the role of consciousness in observation is wrong.  The resulting conclusion will be that quantum theory, while weird, could not have been otherwise.

Indeterminism refers to the randomness that is inherent in quantum theory3.  This is philosophically troubling to many people who expect a completely deterministic world of the type envisioned by classical Newtonian mechanics.  Einstein was among those so troubled, and it was this facet of quantum theory that prompted his famous quote “God does not play dice with the universe”4.

However, we must ask if a completely deterministic universe really makes sense.  Think of the implications of such a universe.  It would mean that every action that has ever happened since the dawn of time, or any action that will ever happen in the future, has been or will be completely preordained.  Every letter I type in this essay, every instance of every person who reads it, every war, every dinosaur mating, every larva pupating, could have been predicted an instant after the big bang, either by God or by some extra-universal intelligence with omniscient data and sufficient computing power.

Does it not make more sense that there is some level of unpredictability in the universe, no matter how small, some level of Epicurean “swerve”5?  However, if the universe is even the least bit indeterministic, then this must manifest itself as some form of randomness, however small.  If the immediate result of state A, ceretis paribus, is not always B, if even sometimes A instead causes C, then by definition there must be a random process that selects in each instance whether B or C obtains.  So it would seem that the first bugaboo of quantum theory, indeterminism, makes perfect sense after all.

In physics the term locality refers to the hypothesis that nothing, including information, can travel faster than the speed of light.  Quantum theory violates this principle with what Einstein called “spooky action at a distance”6.  This feature of quantum theory is manifested most spectacularly in the EPR (Einstein-Rosen-Polasky) experiment, in which quantum-coupled particles separated by arbitrarily large distances seem to be able to communicate with one another instantaneously7.

This ability to send signals infinitely fast defies intuition, but it would appear to be a necessary result of indeterminism.  Consider a particle that has a finite probability of being in two possible places.  If either location could initiate the decision to “locate” the particle there, once one position made this “decision”, it would need to instantaneously notify the other location so that it could avoid making the same “decision”, thus ending up with the particle in two places at once.  It could be that the decision to locate the particle at one location rather than another was made centrally, and then broadcast to the possible locations at the speed of light, in which case locality would not be violated.  But this assumption would violate one of the sacred base assumptions about physics, that the laws of physics are everywhere the same.  It would require the location from which the decision was broadcast to be different than all other locations, since it would be the only one with the power to make the decision.

Thus, it would seem that the assumption of randomness in the universe implies either the need for instantaneous transfer of information, or the assumption that physics is not the same everywhere.  The former conclusion is much more plausible than the latter, and if true, nonlocality is a direct consequence of indeterminism.

The Role of Consciousness in Observation
The famous “Copenhagen interpretation”8 of quantum theory posits that the “decision” to fix a quantum variable (so-called “collapse of the quantum wave function”) at a particular value (e.g., to locate a particle) is triggered by an observation.  While the Copenhagen interpretation does not explicitly state that the observer must be conscious, this assumption is usually associated with that interpretation.  Furthermore, the need for a human consciousness is usually assumed, as is evident by the thought experiment of Schrödinger’s Cat9.

Yet, a little thought reveals how unsatisfactory this interpretation is.  What was the state of the universe before the evolution of human consciousness?  According to this interpretation of quantum theory, the entire universe would have remained in a continuous superposition of states.  Even if this were plausible, how is it that human consciousness was created in the first place, given that a concrete instance of a human would have required the corresponding quantum variables to have been selected?  There is a chicken and egg scenario here, in that human consciousness cannot be created without fixing of quantum variable values, and these values cannot be fixed without a human consciousness as an observer.

What is much more plausible is a variation on the Copenhagen interpretation called objective collapse theory10, in which “there is an ontologically real wave of some sort corresponding to the mathematical wave function, and collapse occurs randomly (‘spontaneous localization’), or when some physical threshold is reached, with observers having no special role”11.  I prefer the latter class of these theories, in which “some physical threshold is reached” that causes the quantum variable to obtain a specific value.  These theories remove consciousness from its role in quantum theory, but still explain how observations can force a quantum variable into a specific state.

The point is that consciousness is not required as a basic tenant of quantum theory.  The role of consciousness in observation is not problematic, because, in fact, consciousness has no such role.

Quantum theory is considered counterintuitive for three reasons, each described above.  However, the first is philosophically implausible, the negation of the second is implied by the implausibility of the first, and experimental and philosophical progress are eliminating the third.  Not only is quantum theory not weird, it makes perfect sense.

End Notes

  1. “Niels Bohr”, Wikiquote, URL=<http://en.wikiquote.org/wiki/Niels_Bohr>.
  2. Orzel, Chad, “The Most Precisely Tested Theory in the History of Science”, ScienceBlogs, May 5, 2011, URL=<http://scienceblogs.com/principles/2011/05/05/the-most-precisely-tested-theo/>.
  3. Indeterminism is not the same thing as lack of causality.  For a discussion of the difference, see my essay on Free Will.
  4. “Albert Einstein Quotes”, GoodReads, URL=<http://www.goodreads.com/quotes/2669-god-does-not-play-dice-with-the-universe>.
  5. “Epicurus”, Wikipedia, URL=<http://en.wikipedia.org/wiki/Epicurus>.
  6. “Einstein’s ‘Spooky Action at a Distance’ Paradox Older Than Thought”, Technology Review, MIT, March 8, 2012, URL=<http://www.sott.net/article/242684-Einsteins-Spooky-Action-at-a-Distance-Paradox-Older-Than-Thought>.
  7. “EPR paradox”, Wikipedia, URL=<http://en.wikipedia.org/wiki/EPR_paradox>.
  8. “Copenhagen interpretation”, Wikipedia, URL=<http://en.wikipedia.org/wiki/Copenhagen_interpretation>.
  9. “Schrödinger’s cat”, Wikipedia, URL=<http://en.wikipedia.org/wiki/Schrodingers_cat>.
  10. “Objective collapse theory”, Wikipedia, URL=<http://en.wikipedia.org/wiki/Objective_collapse_theory>.
  11. Ibid. (“Compared to other approaches”)

November, 2013

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