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Laura Templeman

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what causes collapse of quantum superposition?

It is my understanding that quantum particles exist in a state of superposition until measured.

Question 1: Does this mean the same thing as: quantum particles collapse out of superposition when they interact with another particle?

Question 2: Further if quantum particles in the real world are constantly interacting with other subatomic particles, how would they ever have the chance to be in the probabilistic state of superposition?

Question 2 asked in another way: I understand the Copenhagen Interpretation vs the many worlds. My question is more fundamental than that. Regardless of what happens when the wave collapses into one event, how does a subatomic particle ever stay in superposition except in a vacuum? (Or is that the only place where it actually does happen?)

Thank you to anyone who can answer this. I teach Philosophy 101 and this question came up and I am unsure how to answer it.

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    Oct 25 2013: Hi Laura :) You cause the collapse of quantum superposition!

    Quantum physics - 'Consciousness is trying to figure out Super consciousness'.

    You, as an observer, with brain, are the reason. Let me explain this with the help of an example. How do u see? Some reflected photons travels to your eye sensors and received information are passed to your brain in a very specific format which mind interprets you as light and color. Isn't it strange!, your brain never see the light, always remains in dark but yet it decodes the information as light. Now the doubt of uncertainty raises- WHAT IF OUR BRAIN IS INTERPRETING WRONG? Not only eyes, every other sensor thru which we know our world, are just receptors of different wave(length)/particles and brain has fixed format to decode particular information. Thus no one can really reach to the reality this way (at least using sensors).

    The Particular quantum state is the 'interpretation of our brain'. I dont know how but scientist must observe the state of brain of the observer instead of the object. It is the limitation of our Brain, where information collapses to either this or that. 'Quantum Entanglement' can also be answered by this. Observer’s brain can think faster than speed of light. Knowing the state of other entangled quantum causes collapse. I have an example in my support -

    http://en.wikipedia.org/wiki/Spinning_Dancer

    In this animation the information of spinning girl (clock/anticlockwise), suddenly collapse in our brain after continuous gazing, and becomes (anticlock/clockwise)

    Ans 1: Distance/time is the matter of brain, not consciousness. So it does happen in real time.
    Ans 2: Wave is actually the shifting of energy from particle to particle. 'Probabilistic state of superposition' theory is the outcome of 'Puzzled Brain'. Wave exists as a whole and we cant find it in a particle (by observing). That's why quantum slit experiment fails.

    So, Observing the observe may solve the problem of Quantum physics. :)
    • Timo X

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      Oct 25 2013: What exactly is special about consciousness that it causes this?
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        Oct 29 2013: Hi Timo !

        No! consciousness is nothing to do anything with this. And what so special about consciousness is that it is not special at all. Also we can not define it or explain it bcoz we (humans) do not have anything in our world to relate it, thus hard to understand it. All our definitions belongs to known or experienced things. For example - Flower: the seed-bearing part of a plant, consisting of reproductive organs (stamens and carpels) that are typically surrounded by a brightly colored corolla (petals) and a green calyx (sepals). Timo, do you think one unknown person can know all about flower by knowing this definition. No matter how hard you try to explain about flower, the soul or spirit will always be unexplained. Now what if, you have to explain only the soul or spirit of the flower !

        However, I have found a very similar system in our world to relate and explain it, A 'Computer System'. Think electricity as consciousness of the computer system and all digits, alphabets or special characters are alive figures. These figures have brain to think their own. They found themselves existing and alive, living in folders and files. They are indulge in searching of truth. They are curious to know about them, about colors, about folders and everything happening in their world. Some smart figures (scientists) found that they are pixels. Some other have searched the DNA (0,1).

        How would they found the Truth, The Consciousness, timo?

        You asked what is special about consciousness? I must say, the special or strange thing is the existence of figures, their life, their sensors, their brain,... but not consciousness.
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    B Ross

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    Oct 24 2013: My Interpretation:

    1. Yes to question 1. However, I do prefer to frame this notion slightly differently. I think of classical mechanics as describing the system undergoing superposition. I think that probabalistic behaviours (such as "observed" superposition) never disappear. I think of them as overlapping or superpositioning to produce what we think of as "Classical Mechanics."

    2. To answer question 2, particles always exist in probabalistic states. When they appear not to be in a probabalistic state, its because sufficient composite particle complexity has been reached to overlap probabilities and confine a system to behave according to newtonian or classical mechanics.

    One analogy is imagine deciding where you want to go for lunch on a day when you're alone. You can go anywhere. The next day you happen to be with several friends who are picky eaters, dieters, or maybe have some food allergy. The group now has overlapped probabilities due to the complexity of its composition. The group has restricted its possible destinations for lunch in exchange for adding members to the group. If your group finds a place that satisfies everyone, the probability of going to that same destination everytime this group gets together escalates.
  • Oct 24 2013: I think what you will benefit more is understanding deterministic vs probabilistic approaches to nature, and where they are applicable/more efficient, and of course some good modern physics 101. However, you have asked a technical question, and I will answer technically, I will try not to use formulas, and technical terms.
    1) Probably you are confused by the definition of a quantum "particle". For example, in condensed matter theory, a commonly used "quantum particle" is actually an ensemble of particles interacting with each other, like electrons in a transistor. Thus their "state" is their collective behavior, which includes their interactions with each other. Moving to your question, yes it will. (Technically speaking, it does not need to be a "quantum" system either. For example imagine a ball in a box you can not see, if you want to know the location, the information the ball represents (your state) is the position in space. Since you don't know the place of the ball before measurement, it can be anywhere, so the state of your system is a superposition of all the possible spaces in your box. When you observe it by some means, now you know the position, so the state collapses into one position)
    2) since in real world everything is interacting with everything, everything is constantly "under observation". The constant flux of "observations" in the ensemble are not necessarily compatible with your observation, and thus every state you define through your observation has a finite lifetime. Imagine a Stern-Gerlach experiment where a million other scientists are trying to measure other polarizations all the time. Luckily, their magnetic field can be overridden by yours to some extent. Actually finding stationary states of "quantum particles" are a bigger technical challenge than letting them go decoherent. Please see sideband cooling.
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    Oct 24 2013: Thank you, Fritzie, for an excellent answer, and advice on posting to a science board as well. Your answer demystified things.
    Thanks to the other answers as well.
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      Oct 24 2013: Best wishes with this. As I wrote, the answer I posted was not my own but that of someone who knows this field as well as anyone in the world.
  • Oct 24 2013: I believe it's caused by too much IPA....
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    Oct 23 2013: Laura, here is a reply from a very well known specialist in, and professor of, this field:

    "Quantum particles have very well defined states that don't change in time. But they can be in superpositions of the states. It's actually not as complicated as it sounds. For example,a quantum magnetic "spin" (a little like a microscopic bar magnet) has two possible time-independent states in a magnetic field, labeled spin "up" or "down." But if a sudden magnetic field in a direction is applied, it could give the thing a little kick that starts the magnetic spin rotating between those states, again a little like a bar magnet could rotate.

    With that in mind, we go to your questions.

    1. The interaction could put the system (in our example, the magnetic spin) into one of its time-independent states, but often it won't. It depends on how strong the interaction is and on whether the interaction is magnetic. For example, the magnetic spin on a hydrogen atom may not change even though it collides with something else and its trajectory changes. Similarly, the atom has well defined time-independent electronic states, and those might not change from the collision either. They could, but they often don't, and whether they do or not is probabalistic (you can't know for sure what will happen beforehand).

    2.The interactions might not be that strong, or they might change some things like the trajectory and not others like the magnetic or electronic state. So the particle can remain in a superposition of some kinds of states even when it interacts with lots of other particles. Note that "collapse" can seem mysterious because you might think of something really collapsing or changing form in a dramatic way. Usually it's much simpler. The superposition "collapses" into one of the time-independent states that it was a superposition of. For example the magnetic spin is then in the "spin-up" state, not rotating between up and down.

    Alternate universes are not involved in any of this.
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    Oct 23 2013: disclaimer: don't know. but i present you 3 possibilities that i have read and i find both understandable and common sense. please note that these are actual scientific theories, though probably there no consensus in this.

    1. there is no quantum collapse at all, there is "entanglement". observation merges the observer and the observed into one big system, and quantum uncertainty now applies to the whole system. please note the asymmetry in the complexity of the observer (scientist) and the observed (particle). so it does not mean that the uncertainty "spreads" to the observer. but quite the opposite, the observer's "rigidity" will somehow (i don't know how) spread to the particle.

    2. the quantum collapse does not happen when the particle is observed, but slowly happens on its own. how slowly depends on size. a photon practically never collapses, it would take many millions of years. for a system as complex as a biological organism, quantum collapse happens in an unmeasurable time. as you observe the particle, you merge into one system (similarly with option 1), and thus the collapse happens instantly. more on that: http://en.wikipedia.org/wiki/Orch-OR#Details

    3. there is no quantum uncertainty at all. the quantum theory is only a probabilistic description of the world, and the uncertainty really just means, we don't know. but the particle is in a definite state all the time. this theory seems to refuted by the observationally proven bell inequalities. however these observations contain loopholes http://en.wikipedia.org/wiki/Loopholes_in_Bell_test_experiments (especially the Fair sampling assumption part). this makes it possible that quantum uncertainty simply does not exist.
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    Oct 23 2013: You discuss quantum physics in philosophy class? Do you find other applications for it (digressions on reality, on time, on life), or is it confined in the strange laws of physics?
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    Oct 23 2013: Laura, for reliable information on a question like this, be sure also to post on a science site. We do not have many physics specialists here, and there is a lot of misinformation floating around the internet on quantum physics.

    That said, a specialist in quantum mechanics from a major East Coast university happens to be visiting and says he will answer your question for me tomorrow.
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      Oct 23 2013: This is what everybody says in Sword in the Stone. Yet "let the boy try" is the voice of reason.
      So here goes :

      1/ No they don't collapse when they interact with one another. A single observed particle will behave as though something had bumped into it and changed its course and this commotion, when more particles are in play, mimics the commotion of a wave. However, this "wave" of possibilities that represents all outcomes in the multiverse is reduced to a single particle's trajectory when a single particle in a single universe is observed, for obvious reasons.
      2/ A particle remains in this superposition state until you make an observation, because you can only make an observation in one universe, even though you can't explain the outcome if you rule out the existence of the other universes.