Do superpositions violate conventional logic (philosophy)?

Maui

This is not just a problem of conventional logic, it's more like a deep epistemological abyss, as conveyed by the inability of physicists to understand what things(objects) are. It could either be a limit to knowledge or a deeply rooted misunderstanding that we carried on through the centuries.

xts

1. Have you ever seen any pattern extending to infinity?
2. Even if so - where is inconsistency?
Natural numbers extend to infinity and they are "discrete" if you look at them with real numbers in a background.
Of course, infinite pattern must be composed of infinite number of "discrete" elements, the same way as finite pattern is composed of finite number of discrete photons.
But "infinite number of distinct elements" is not an oxymoron.

Maui

I don't have to. You have never seen an electron, yet you can measure and deduce its properties. The probability amplitude peaks at a definite point in space and becomes zero everywhere else only after a measurement is done. This has been experimentally verified and implemented in a number of applications.



There is clearly the contradiction that LostConjugate spoke about - it's a problem of classical realism and lots of human baggage. But to say that there is no contradiction with our everyday concepts when an electron interferes with itself, is an exaggeration.



Thinking of an electron in motion towards the detector plate as an "infinite pattern" and then interfering with itself gives everyone a headache. If you think you understand how a single electron can pass through both slits at the same time, that's a solid indication that you don't understand it.

xts

Really? Isn't all that contradiction contained in intuition baggage depicting an electron as an electrically charged snooker ball?
I just don't think about "single electrons passing through anything".
I think about electron existence only at the very beginning (as it is emitted) and at the very end - as it is detected. So it is not electron, which interferes with itself, but wave function. Wave function or whatever else you like to use in calculations - are artificial concepts, useful to predict experimental results. Like a "gravity force" is an artificial concept helping to predict Moon eclipses.

Maui

Most certainly.



This works for removing contradictions, but if we can't understand what matter is, we are in no better position to know the world than we were in the Stone Age.
It seems to me that most physicists have now tacitly accepted that reality happens(essentially giving up realism) as opposed to reality exists, without going deeper what it all means(or they simply don't like the implications or are too shallow to follow the ramifications through till the end).

wuliheron

Indeterminacy is at the heart of superposition and what Indeterminacy does is challenge the law of identity. More recent evidence that even entanglement is subject to Indeterminacy again places the focus squarely on the law of identity suggesting that either our definitions of quanta require revision, the law of identity requires revision, or both. Which it might be is anyone's guess at this point.

I'd compare it to the discovery of the constancy of the speed of light which seemed to defy conventional logic and the known laws of physics. At the time nobody knew if logic required revision, the laws of physics, and or their definitions. We could speculate endlessly, but there is no clear evidence yet that supports any one view.

UChr

It is not impossible to imagine that we extend QM with various unnecessary ideas and concepts and thereby achieves a local 'realistic' description of the double-slit problem.

First postulate: the space is not empty - with dark matter and dark energy it is not so unlikely - but then we have the ether back.

Second postulate: particles creates waves in the ether corresponding to QM's descriptions.

These waves create possible interference.

These wave guides the particle.

I think De Broglie thought something like that - But Bohm build a deterministic theory upstairs?

Most physicists would say that these decisions are ugly and unnecessary when they do not make any measurable difference.

Maui

Local realism lives in the classical world, and usually it's a shock the first time people hear of there being no classical substance in this reality at all. It's an incomprehenisble quantum "substance" that strains towards classicality via processes like decoherence, collapse, symmetry breaking, etc. Observed local realism is the end result of fields acting in a classical-like way.





Yes, they are the crutch on which realism as we know it, is supposed to hold. But I'd say that the BI adds more mystery than it removes. Classicality is deceptive, there's many a wrong path to take. No wonder physicists need an infinite number of worlds to explain ours(or rather explain it away).

jambaugh

amblerise,

The article's phrasing of " ... simultaneously being 'a' and 'not a'..." is very bad poetic license attempting to describe quantum superposition in classical vernacular.

It is important understand that the term superposition is first applied, not to the quantum system, but rather to the measuring devices. Consider photon polarization for a moment. You can have a Polaroid film in front of a photon detector so that it will only click for vertically polarized photons and never click for horizontally polarized photons. By "vert. photons" etc we mean photons which have already passed through a vertical polarizer and likewise with all other "states". Note that we cannot know anything about the photons except in how they behave with respect to measuring devices. But what we see is that all photons will either pass through a vertical polarizer or through a horizontal polarizer. So it would seem that photons only come in two states, horizontal and vertical.

Then we look at them all again 45deg turned and notice that all photons are either left-oblique or right oblique. The oblique polarizers, as measuring devices, are superpositions of the vert/horiz. polarizers. A photon measured with vertical polarization will sometimes pass through the left-oblique and sometime through the right oblique. (Note we can non-destructively determine which with a birefringent crystal such as calcite.)

This lead us to abandon (at first) thinking in terms of the photons as having an objective state independent of our choice of measurement. We simply identify photons as phenomena (not objects) which behave in a probabilistically predictable way.

That plus some other points is the Copenhagen Interpretation. Now other interpretations try to build a more involved "reality" of the photon below what is observable, e.g. many worlds and pilot waves.

To avoid confusion about the logic of quantum mechanics it is important to stick to only statements about what has been or will be observed and forget about statements about the state of the system excepting as they translate to what has been/will be observed.

yoda jedi

superpositions can be break if nature is nonlinear, nonlinearity break the linearity of the superposition.


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UChr

I think that 'many worlds' is a relatively funny science fiction idea.

I do not understand how it can be taken seriously.

jambaugh

Yea, the one thing that grates on my nerves when I watch SciFi programs is when the "science expert" inevitably says... "yes, quantum mechanics predicts an infinity of parallel universes...". I go AHHHHRRRRRGGGG!!!! NO IT DOESN'T and throw pillows at the TV. Too many people grow up hearing this because it makes the best premise for the "magic" in these fantasies.

The writers could at least change it to "... one interpretation of QM predicts...".

In Everett's defense, there is some virtue in his "relative state" approach and I want to spend more time looking at his original thesis rather than the MW into which it evolved.

LaurieAG

A superposition is a transition phase, with a probability of 50 percent, which results in either a positive or a negative observation. It's not really an end state like the probability of a tossed coin sitting on its edge but more like an intermediate phase between one outcome and another.

If you look any closer at the transition phase it implies an initial state, a transition phase, and an observed state with a range of change from its initial state of 0 or 1 (i.e. True, transition, True and False, transition, False have no state change while True, transition, False and False, transition, True have a total state change).

Could a quantum superposition be considered a start state?

LaurieAG

The following is a good example of ambiguity "while some people think that black holes are portals to other universes, in reality they are just exceedingly dense pricks".

ThomasT

This is, imo, just a bad way of talking about the formalism.

Conventional logic still holds. Just don't make the mistake of thinking of mathematical quantum states or superpositions as real states, ie., of descriptions of what's actually happening in the underlying reality.

Then you've just misunderstood the essence of the Copenhagen Interpretation.

The quantum theory is a probability calculus. Quantum superpositions are expressions of experimental possibilities. There's no implication that "the particle is in two places simultaneously", or that "the particle exists and doesn't exist simultaneously", or whatever.

Maui

...because your obviously classical mindset can explain the quantum? You know what they say - "If i haven't seen it, it doesn't exist!". If it doesn't behave according to my predjucies it's not real(even though the registered pattern on the screen of the double slit experiment is obviously a result of a something passing through both slits simultaneously). As far as i know, for very good reasons, the whole 'particle' way of thinking was found to be a misconception more than half a century ago.





That's your philosophy and it's acceptable and it's right where it belongs. But if you come to really think about it, the classical mindset is not a gift from god, it's likely a misconception(as evidenced by the philosophical implications of SR too)

PS. If superpositional states aren't real, what is this underlying reality you speak of? It sure can't be real as far as a classical mindset can grasp it. An equation?

ThomasT

What I'm saying is that quantum superpositions don't violate conventional logic in the sense that it was conventional logic that led to their formulation, and that they also don't (in and of themselves wrt their form and content) violate conventional logic as long as one takes them as what they are (expressions of relationships between and among instrumental possibilities) as part of a mathematical formalism designed to generate statistical probabilities wrt instrumental behavior, and doesn't attribute any deeper significance to them.

Our mindset is necessitated and constrained by our sensory capabilities. So is our capacity for explanation, understanding, and unambiguous communication.

But given those limitations, it doesn't necessarily follow that the deep reality must be essentially different from the reality of our sensory experience. That is, I like the assumption that there are fundamental dynamical laws governing all physical realms, and that apparently scale and realm specific organizing principles have emerged from those fundamental laws.

What misconceptions do you think are "evidenced by the philosophical implications of SR"?

Nobody knows what the underlying reality is. Nobody can know. Which is precisely why quantum superpositions shouldn't be taken as referring to the underlying reality.