Word of the Week Wednesday 1/11/12

by Max Andrews

The Word of the Week is: Quantum-Logic

Definition:  An interpretation of quantum mechanics developed by John von Neumann in the late 1930’s.  Quantum logic says that everyday logic cannot be applied to the quantum world.  Contrary to Boolean logic, quantum logic says that and and either do not have the same meaning in the quantum world.

More about the term:  This interpretation isn’t known to be deterministic or indeterministic.  That is still up for debate.  However, there is no collapse of the wave function.  Also, local causation is uncertain as well.  There is little debate on the issue but the majority understanding of this is that it has a unique history (contrary to other non-collapse interpretations like Many Worlds).  When using Boolean logic to assess quantum logic it may seem that quantum logic is self-contradictory; however, if quantum logic is assessed internally it is indeed consistent.  The major problem for this system is extrapolating applied logic.  Boolean logic is certainly valid in everyday life but is invalid in the quantum world.  One way or another it seems that contradictions may arise somewhere along the way.  For more information see John Gribbin’s Q is for Quantum.

Example of use:  Consider the double slit experiment where a photon is shot at a wall with two slits and the photon goes through either one (or both).  So, because there is no wave collapse the photon actually goes through both slits.  There’s a different logical significance in this experiment.


3 Comments to “Word of the Week Wednesday 1/11/12”

  1. It’s interesting that Q-logic is still logic and not some irrational rant about how 2+2=5.

  2. I’m a bit confused by the term ‘quantum logic’. ‘Quantum logic’ seems to be the kinds of operations used in quantum information theory, that have some similarity to the operations of Boolean logic like AND or OR. But I don’t think any philosopher would argue that quantum logic is some kind of alternative to classical logic of the kind used in philosophy. The main reason is that ‘quantum logic’ is based on physics, not metaphysics. For instance, when we say that -on QM- a particle can be at point A and point B simultaneously, that does not contradict the law of the excluded middle because we’re not offering a logical proposition. Our statement would be precisely the same as saying that an ocean wave can strike two points of the shoreline at the same time. The physics of a wave render it possible to have this non-local behavior without entailing any kind of logical contradiction. Admittedly, the laws of QM are more counterintuitive. But -as far as I know- they still do not lead to outright logical contradictions.

    • I agree, it doesn’t really advance the understanding of QM. Especially since it doesn’t deny collapse there are other interpretations that aren’t as extreme as this. Hey, I’m more sympathetic to many worlds interpretation than this one. For some reason many physicists think excluded middle is divorced from QM.

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