Talk:Quantum superposition

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Is superposition native to any specific interpretation of quantum mechanics? How does the Kopenhagen and the Many-worlds interpretation deal with superposition respectively? -FredrikM kauss-at-aland.net

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User:65.104.118.82 added this text:

Alternative theory for the layman:

Although non-rigorous, another explanation may help the average person form a mental image of how a quantum object can have more than one value at once.

Since the speed of change between objects is limited by the speed of light, the smallest time interval that an object's characteristics can be measured ( or observed ) is also limited by the speed of light.

If we imagine a string that is vibrating at a frequency billions of times higher than light itself can travel in a nanometer, then the phase (position of midpoint) of that string would appear random every time we attempt to observe it. It would appear as if the string was holding all values until the observation event, at which time it would have only one value. This would be similar to a strobe light on a spinning fan.

When objects are connected with entanglement, this ultra-high vibration of one object is linked to its entangled partner such that there is a relationship between their quantum values. If there is a series of entanglements, then a quantum computation could occur.

Before the event of observation, the initial object would vibrate thus affecting its entangled partner at change rates far higher than the speed of light would seem to allow. Perhaps in the quantum foam, this is allowed ? In any case, qubits that are tied together are exercised through their entire range seemingly simultaneously, thus giving the impression that the output can have all values.

However, the way you get a single-valued answer out of a quantum computer is to observe the inputs over and over again until the right pattern is found. This "input search" will give the correct answer on the output when the inputs have been matched to the quantum computation machine. Each observation of the input set collapses all of the input objects' entangled partners (and their partners) thus collapsing the output to a single value.

A promising area of research is "functional entaglement" such that an object's state is a complex function of its partner's state, not simply a duplicate. This allows fewer qubits to achieve a specific formula.

This seems like unsourced original research to me, which is already enough to prevent inclusion in the article. It's also very confusing: what does vibrating at a frequency billions of times higher than light itself can travel in a nanometer mean? It should obviously be either the time it takes light to travel a nanometer or the distance light travels in a nanosecond, but neither one of those makes much sense either. Is the string actually moving faster than light or not? —Keenan Pepper 02:35, 30 June 2006 (UTC)

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I see your points. Well taken.

In the interests of keeping it short, I took too many liberties with the explanation. Maybe this can help:

The quantum object is not "vibrating" in the physical sense, but changing its internal characteristics. This change in characteristic is not movement, so it is not limited by the speed of light. It changes its internal state at orders of magnitude far higher than any possible physical observation can take place. (Observations are limited by the speed of light).

Because the rate of cycling through its entire range of possible characteristic states cannot be followed by fast sequential physical observations, it appears random. In the time that light moves in a nanometer (smallest distance we typically can observe), the state of the "uncollapsed" quantum object has already been through vast numbers of cycles.

The point being is that while there is no way to prove this theory via direct observation, the "simultaneous value" assumptions being used to describe some quantum phenomena may imply incorrect features in quantum computing. This alternate perspective may allow other avenues of thought in the goal of obtaining useful qubit results. —The preceding unsigned comment was added by 65.104.118.82 (talk • contribs) .

Okay, let's look at everyone's favorite example, the double-slit experiment. In this experiment, the electron has some probability of passing through either of two slits, so its position has two possible values. In your interpretation, the electron is moving rapidly back and forth between these two positions, which are separated by a macroscopic distance (say, a millimeter). The problem is that if the electron were moving back and forth, its kinetic energy would be much greater. Where would this extra energy come from? Also, your model doesn't explain the observed outcome of the experiment, which is that the electrons make a diffraction pattern on the screen, even if they are so infrequent that only one of them at a time is going through the slits. How can the electron interfere with itself as a wave if it's just moving rapidly back and forth? —Keenan Pepper 04:13, 30 June 2006 (UTC)

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It is not moving back and forth in the physical sense. The internal characteristics are not the same as the external states such as electric charge, spin , etc. The internal characteristics arise from similar forces that allow quarks to interact. As an analogy, the speed at which you can change your mood is not related to how fast your body is moving.

But the electron has two different values of its position, an external, measurable property. How does your interpretation explain that?

.... All external properties are derived from the fluctuating internal properties at the exact moment of observation. Think of quantum particles as more like gas giant planets rather than rocky core planets. There is no surface boundary of a gas giant. An electron can be spread out in several places because its equivalent of an atmosphere is spread out. (pardon the wild analogies, but I hope to explain, not prove)

All right, this is definitely a nonstandard idea. What internal properties determine the external property of position, specifically?

Also, if the particle is spread out like a gas giant planet, that explains superposition by itself, and there's no need to bring light-speed fluctuation into the picture.

Also, electrons are not made of quarks.

.... I was not referring to quarks per se, but of the forces between them.

All right, what do the forces between quarks have to do with the internal characteristics of an electron?

Every quantum particle emits a field. Some particle fields have very short distance effects (i.e. nutrinos) and some have long distance effects (i.e. electron). After all, particles are nothing more than highly concentrated fields in which the concentration density gives the mass. Without fields there is no interaction possible.

In the double slit experiment the electron field outer fringe passes through the slit "before" the core. When the two parts of the leading portion of the field interact, it sets up a standing wave thus guiding the core one way or the other.

What do you mean by "core"?

.... There is a continuum of field concentration density from the outer fringe to the core. The core is the area of highest concentration and typically though of as the position of the particle. However, the core is not necessariy spherical, but could easily have the shape of a peanut shell.

But in the double-slit experiment, just after it passes the slits, the probability function for the electron's position has two maxima, one in front of each slit. Which one is the "core"? Or does it have two cores?

As the slits get closer to each other, the standing wave gets more definition and the interference pattern is sharper.

The fields I am referring to are the same ones that give rise to the quantum foam, where virtual particles spontaneously appear and disappear.

It would be interesting to see how much "faster" this field is compared to the speed of the particle. An experiment could be set up where a moving point charge is aimed at a stationary point charge of the same type, but at a slight angle as to cause a glancing blow. By varying the velocity of the moving charge and detecting where it begins to alter it's trajectory (taking momentum into account) it may be possible to time how long it takes for the particles to "recognize" each other and deflect.

This experiment would have the most interesting results if the moving particle was very close to the speed of light. —The preceding unsigned comment was added by 65.104.118.82 (talk • contribs) .

I have no idea what you mean by "the speed of the field" versus "the speed of the particle". How would the measurement in this experiment be performed? —Keenan Pepper 19:22, 30 June 2006 (UTC)

.... The field emanating from the particle is either at the speed of light or faster. If faster, it cannot be one of the familiar physical field such as electromagnetic, weak, or strong forces. The fields at play in the quantum foam that allow interactions between the virtual particles and between entangled photons certainly seem to be faster. The jury is still out on gravity.

This experiment could only take place in a particle accelerator. While the trajectory of one particle could not be tracked conclusively, a steady narrow stream might. First, measure the deflection of the stream at slow velocities like one-third the speed of light. On a flat target detector behind the stationary point charge, measure its deflection. Next, increase the velocity of the particles in the stream.

If the deflection goes to zero as you approach the speed of light, then there is no interaction faster than the particle itself. If there is a deflection (at the highest speed of the accelerator) and it is related to the strength of the stationary point charge, then there is some kind of interaction faster than the speed of light. Re-stated, does the deflection vary with the strength of the stationary point charge when the stream is at its highest speed possible ? ( at least 99.99% of speed of light in a vacuum).

It will be hard to separate out the effects of relavistic momentum at those speeds, but if we use heavier particles at slower speeds with the same momentum and same charge, it might act as a control reference (use a heavier isotope of the same ionic element). Keep in mind that we are trying to avoid actual collisions.

—65.104.118.82 22:34, 30 June 2006 (UTC)

I don't see how interaction at high beam energies (high particle speeds) implies interaction faster than the speed of light. Could you explain why you think that? Also, how in the world could you "avoid actual collisions"? I work at a nuclear accelerator, and I've seen the spot the beam makes on the target: it's a few millimeters across. There's no possible way to aim a beam at an individual atom, not to speak of one side of an individual atom. —Keenan Pepper 18:26, 1 July 2006 (UTC)

...... It would be similar to fighter jet flying through a canyon at the speed of sound. The pilot would never hear the echo of his jet. The results of the sonic wave interacting with the canyon wall would never catch up the the speeding plane.

If the distance between the moving particle's wavefront and the particle is less than the distance between its trajectory and the interaction point, then there can be no interaction felt by the particle (unless it is a collision). If the fields don't interact directly with each other, but only on the particles themselves, then the existence of the stationary field before the moving particle arrives should not matter.

Okay, now you're ignoring the principle of relativity. Sound waves move through a fixed medium: the air. They used to think electromagnetic waves also moved through a fixed medium (see luminiferous aether) but now we know that's false.

While I agree that getting this kind of accuracy would be very difficult, the beam could be narrowed with a hole in a thick layer of particle absorbing medium. Perhaps some kind of technique similar to integrated circuit lithography. (for electron beam type, not the UV type)

No, a narrow hole would make the beam spread out more. The particles that made it through the hole would come out the other side in all different directions. Confine the position and the momemtum becomes undefined: that's the uncertainty principle.

Besides, you don't really have to eliminate the occurence of collisions, just remove their effects from the analysis. A crescent or donut shape will form. The important measurement is the inside radius of the crescent/donut.

—65.104.118.82 22:34, 30 June 2006 (UTC)

Tell you what. Go take some courses on relativity and quantum mechanics, write these ideas up in a paper, and publish it in a peer-reviewed journal. Then I'll read it. —Keenan Pepper 19:26, 3 July 2006 (UTC)

If you don't like my comment, make an intelligent reply to it, don't vandalize this page by removing it. —Keenan Pepper 21:05, 3 July 2006 (UTC)

.... very well. The sound waves in air analogy was to illustrate a relationship at the boundary conditions - I am familiar with past ideas of aether and relativity. While its clear that a non-photon particle cannot hit the speed of light without infinite mass, there will be some time required for the interaction to catch up to the (almost) light speed particle. That would be evident in the deflection difference even it if is only a very small amount. This explains why a photon is only affected by gravity (and matter).

Ok, forget the hole. In whatever manner, the beam diameter and particle flux should be minimized at high energies. In any case, I am not an experimental physicist like yourself. Hopefully someone could create a valid experiment in the future. To get back to my original point of simultaneous values in a quantum computers, there may be alternative perspectives.

Someone just pointed out at Talk:Fermat's Last Theorem that an article's talk page is not the appropriate place for general discussion of its topic. Article talk pages should only be used for discussing possible improvements to the article. If you want to continue this discussion, let's do it at my user talk page. —Keenan Pepper 19:16, 5 July 2006 (UTC)

ok.

[edit] Lead

Any chance of including in the lead a more layman-friendly explanation, just a sentence or two before one gets to the details? zafiroblue05 | Talk 04:14, 19 May 2008 (UTC)