[Monty22]

*heavy duty Quantum light physics*

Ok, I do want to discuss it further some..

Now I had heard of the interfernce experiment plenty of times with the two slits. For some reason, I had not heard the part where a detector on one of the slits will cause the wave form to collapse into particle.

Now what I'm wondering, does the detector itself cause it, or is it our measurement of that detection? If it's the former could you setup a computer to do all the collection of data, and not look at the results, just have the computer know? What if you looked just to make sure the data doesn't change? Would that collapse the wave?

If it's the latter, and only collapses when a living thing views it, would it simultaniously collapse if you stored the data on cd's in seperate parts of the world?

The 'data' I mean is the results of which slit the photon traveled through. I know this has analogues to "schroedinger's cat", but I also wanted to discuss what would it mean if humans (or dogs, cats?) are required for light waves to collapse.

[Damocles]

...go through both slits and interfere with itself.

As a lad, I was told I'd go blind if I didn't stop interefering with myself. Some photons have all the luck...

[VadeRetro]

Any interaction at all with anything absorbs the photon and collapses the wave function.

The perhaps best-educated guess as to what is going on: John Archibald Wheeler thinks the real nature of the photon is elusive to our ability to sense it. It's something sort of in-between that we cannot detect directly; we can only detect wave phenomena or particle phenomena so it looks at times like one and at times like the other.

[petuniasevan]

PING for your expertise on the subject.

[AntiGuv]

Quantum kitty placemarker!

[bondserv]

A well known Senior Stanford Research Physicist's take on light.

Article here.

[LiteKeeper]

read later

[Nick Danger]

How many Heisenbergs does it take to change a light bulb?

If you knew the answer, you wouldn't know where the light bulb is

[TheBigB]

I know someone who might be able to help...*pings*

[azhenfud]

Must be working on a Slits Light.

[Hank Kerchief]

Well the answer is that the photon travels as a wave and does somehow manage to do what seems quite impossible and go through both slits and interfere with itself. If we cover one slit then we know which one it goes through and indeed the interference patterns vanish. Even more strange is the fact that it we put a detector on one of the slits to tell us whether the photon goes through that slit or the other one then the interference pattern vanishes. The act of observing the electron makes its wave nature collapse into a particle.

I don't think this is quite correct. I pretty sure you cannot get an interference pattern with only one photon. I have always had the impression this experiment was a bit misleading. There is an interference pattern, which is the distribution of photons. If there is only one slit, the photons are distributed somewhat evenly. If two, they are distruted in what appears to be an interference pattern.

As for a detector being on only one slit, it's obvious, if a photon is detected at the slit, it doesn't go through the slit (or at least past the detector). What does it mean to "detect" a photon. They don't make a breeze.

Why do you suppose there is nothing in the literature about putting a detector on both slits?

Hank

[Flashlight]

You have *got* to read the book Schroedinger's Kittens by John Gribbin:
http://www.amazon.com/exec/obidos/tg/detail/-/0316328197/103-5397084-2448641?vi=glance

[Physicist]

Would light always be a wave if nobody was there to observe it? If a dog observes the photon will its wave function collapse? This will lead us to deep philosophical questions and eventually we will be forced to ask whether the universe only exits because there are intelligent beings to observe it.

Any interaction that transfers information about the state causes the wavefunction to collapse. For some measurements, a single atom of impurity in a crystal is sufficient. There is no requirement that a quantum mechanical "observer" be conscious.

[rface]

Would light always be a wave if nobody was there to observe it?

If a tree fell in the woods, and nobody heard it would it still make a sound?

Is light a wave or a particle within a black hole?

[Lessismore]

With two slits, you get an interference pattern. With one slit you get a diffraction pattern. The latter is not a single line.

In college optics the use of a laser made the experiments a lot easier to do. It may work to shine one of those laser pointer gadgets through a narrow slit in an index card and observe the diffraction pattern on an index card beyond that. Try about 2 feet from the laser to the index card, and another 2 feet to the target card.

Then repeat with two slits about an eigth of an inch apart.

[ko_kyi]

I have absolutely zero understanding of quantum physics, or close to zero anyway.

Someone once gave the example of a thermometer. If you take an ordinary mercury thermometer you can get a pretty accurate measure of the temperature of a bathtub or even a saucepan. If you try to measure the temperature of a 1mm drop you don't do as well because the drop quickly becomes the temperature of the thermometer. When you try to measure very very small effects it becomes difficult to do so without applying some change to what you are measuring.

[NorseWood]

bump