As long as the measurement device is on and recording, the state will be altered. (published on ) Follow-Up #6: Quantum for the non-scientistĪny measurement process that has a permanent effect on the system of interest causes the collapse of the wavefunction to a particular state, regardless of whether/how the results are interpreted by a human being. As is common in cases of confusion, some people use the occasion to claim to be the center of the universe and to have magical powers. So people have good reason to link these effects and to be very puzzled by the whole business. That's what converts the quantum spread into quantum uncertainty. The detailed result is purely random, not guided by any prior content of the universe. As to which particular little range of, say, x it collapses to, there's just a probability rule. It's as if the wavefunction "collapsed" in a way guided by the type of measurement made. Likewise if you measure k, the output has a narrow range of k. If you set up apparatus to measure x, you see an output that has a very narrow range of x, even if the input is a big spread of x.
#OBSERVER EFFECT FULL#
What's weird about quantum waves, though, is that when they're "observed" or "measured" we don't see the full spread that was there in the wave. We don't call this "uncertainty" or make a philosophical fuss about it because, as you can see by eye, the spreads in position and wavevector are real, persistent things. The classical wave simply must have spreads in both these attributes, just as you can easily picture for water waves. That says that the spread (Δ) in the wavevector (k, sort of the inverse of the wavelength) times the spread in position (x) is greater than or equal to 1/2. Mathematics requires that any wave, including purely classical ones, have a "spread" relation: ΔkΔx >= 1/2. Nevertheless, there is a relation between the "observer effect" and the uncertainty principle. At any rate, the structure of quantum mechanics, in particular its violation of the Bell Inequalities, would run into big trouble if the random outcomes of quantum events were influenced by any local variable, including human will. Of course, the only events we are aware of are those of which we are aware, but we can leave that worry for the philosophers. us) does something different than interaction with any other large object in which some record is left of the results. Right, we have no indication at all that interaction with conscious beings (e.g. (published on ) Follow-Up #5: confusion between the uncertainty principle and the observer effect Thus since the peculiar randomness of quantum events undermines the deterministic picture of the world it could be said to indicate a sort of "freedom", but not anything resembling traditional "free will." However, the existence of any such will would violate the theorems as much as any other determining variable. On the other hand, when we think of "free will" we have the sense that there was some prior "will" which determined what we chose to do.
That doesn't mean that the necessary determining facts are hard to find it means they didn't exist. There are serious reasons (including the violation of the Bell Inequalities) to conclude that the sort of events described by quantum mechanics are "free" in the sense that no prior fact about the universe can tell us which outcome we will observe. Readers should be forewarned that what follows somewhat spills over the edge of physics into philosophy.
#OBSERVER EFFECT FREE#
Just to expand on a point mentioned in passing in that article, there is a strong distinction between the indeterminacy described by the theorem and the traditional concept of free will. Measurement of the electrons path fundamentally changes the outcome of We could somehow tell which slit the electron went through each time, That the electron can take are not distinguishable. Superposition of two "states", one that goes through one slit, one thatīehavior, this interference will only happen if both possible paths Nature, and is well described by thinking of each electron as a Pattern" for these electrons is evidence of their dual wave-particle That some positions on the screen will have been hit by many electronsĪnd some will have been hit by none. Repeat this experiment lots of times with lots of electrons, we see Wall, how it will bounce, and what it will do afterward.įire an electron at a plate with two closely spaced slits in it, andĭetect the electron on a screen behind these slits, the behavior of theĮlectron is the same as that of a wave in that it can actually go When we throw a baseball at a wall, weĬan predict where it will be during its flight, where it will hit the Objects (like electrons, for example) is very unlike the behavior ofĮveryday things like baseballs. In quantum mechanics we learn that the behavior of the very smallest
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