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Double-Slit Experiment in Time, Not Space
TheMatt writes "Thomas Young's double-slit experiment is a classic experiment that helped establish the wave-like nature of light. Since then, it has been done with atoms, buckyballs, and biomolecules. It has even been seen in a single molecule, and the single electron version was voted the most beautiful experiment by Physics World readers (covered previously on Slashdot). Now, PhysicsWeb is reporting that Gerhard Paulus and coworkers have conducted the double-slit experiment using a double-slit in time, not space. The "slit" was a crafted femtosecond pulse consisting of one-and-a-half cycles--say, two maxima and one minima--passed through an argon gas. Each maxima has a probability of ionizing an argon atom and producing an electron. The electrons were accelerated to a detector which observed an interference pattern since the detector had no idea which maximum produced the electron."
"Adressen på den hjemmeside, du ønsker at finde, er enten forkert, eller også eksisterer hjemmesiden ikke længere. Du kan prøve følgende:
Tjekke om adressen er stavet rigtigt. Bemærk at det har betydning, om du bruger store eller små bogstaver!"
that may as well have been the writeup, because i don't understand a word of it.
Ever read a biography of Feynman?
The very thought of making 5-femtosecond laser pulses (0.000 000 000 000 005 sec, right?) leaves me feeling dumb and slow.
That aside, someone please clue me in here:
So if the electrons hit the laser when the pulse was at maximum strength they would hit the detector, like the two "beams" of light passed through the slits in Young's experiment? and the ones that pass "between" the maxima and minima get distorted like the blurry edges of the light? thus making "slits" of electrons but at instants in time instead of separate points? (I'm no physics expert but I'm sure you guessed that by now...)
You can hold down the "B" button for continuous firing.
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Put simply:
R[\psi_1+theta_c] =frac{\pi^2 \alpha_s^2
}{4320} X^2 (26Y-21r^2+10r^4)^2 r^2
(1-r^2)^{3/2}angle O_1 && psi_1} \langle O_1
\rangle_{\eta_c} }%{ m_c^{10}}.
Now get out your crayon and solve for H.
Yes.
... I guess it became too technical, oops.
You can read more about the double-slit experiment at wikipedia.
Similar intereference patterns(in time and space) are (relatively) trivial to do with light waves/particles. The other experiments mentioned in the article are instances were these are done with matter, and heavy matter for that matter.
For this experiment, consider an atom that would be ionized, once a strong enough laser is shined[spell?] onto it. These guys, as I understand it, have crafted a laser pulse (think of it as a flow) that goes up, down, and then up again. For the first part, when the laser gets strong enough while it "flows" through the atom, an electron *might* come out, then for the second second maximum, another electron might come out. In the end there will be [two?] one, or zero electrons coming out of this atom, but quantum mechanically there is no way to say which came from which bump in the flow.
What the electron detector detects in the end, again I guess, will be a variation of the detection rate as a function of some phase parameter that looks like an "interference pattern " [read "oscillations"]
10 years ago this experiment would still be a "though experiment".
"I've been trying for years to do the double-slit experiment. Alas, the wife still won't go for it."
"That's a pity because your nanoscale penis is probably about the right size for quantum effects to be significant. "
That burnination was worthy of Trogdor himself.
There are 01 kinds of cars in the world. The General Lee, and everything else.
shuddup...heh
i know the parent poster had humorous intent (which he was succesful at)
however, this really is news for nerds.
and to me, it matters.
Very interesting read.
The experiment is the same as a known one, with a single difference: In the traditional experiment the slits are separated by a difference in the normal 3d space, But in this experiement the slices are at the same place in the normal 3d space but separated by a difference in time.
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To demonstrate this, find a sink with two distinct taps. Half-fill the sink with water. Now, turn the taps so that the water drips out slowly from each. You will see ripples spreading out from where the drops strike the water. You'll also see that where the ripples cross, there are light patches, dark patches and some areas that seem to be smooth.
The light and dark patches are where you have constructive interference. If you have a trough, then the trough is deeper than normal and hence appears dark. If you have a peak, the peak is higher than normal and appears light.
the "double slit" experiment was devised by your typical mad scientist. The idea is simple enough. You direct a stream of photons at one of two very narrow gaps. You then have some sort of screen on the other side for the light to shine on. If photons are just particles, then they will go through that one gap and show up as a single spot on the other side.
If, however, particles are waves, they will go through BOTH gaps. The waves will then interfere with each other, as in the sink experiment above, and you'll see patches of light and dark on the other side.
What you get is patches of light and dark, showing that light behaves like a wave.
Now it gets really fun. Turn down the light source. If light is a wave, you expect the same interference pattern, only dimmer. Err, no. What happens is that you start getting a speckled pattern. Eventually, the bands dissolve entirely and you just get a single spot. This proves that light is a particle.
There are a number of ways to resolve this apparent paradox. The simplest is to say that light is a particle that can exist anywhere in the wave with a given probability. With enough particles of light, you see a complete wave, because every possible part of the wave is occupied. With insufficient particles, you get an incomplete wave, and therefore the incomplete interference pattern that you observe.
Now we've got the spacial part over with, we move onto time.
The experiment demonstrates several things. Firstly, it demonstrates that time behaves in a similar manner to space, with regards to objects travelling through it. This will really irritate physicists who have argued that although time and space are coupled, as per Einstein's space/time model, time was not a dimension in the sense that spacial dimensions were. That's going to be a much harder line of reasoning to maintain, now, because clearly time DOES behave in the same way as a spacial dimension, when it comes to diffraction.
The second - and more important - thing that is shown here is that objects do not just have a probability of existing in a specific point in space, they ALSO have a probability of existing in a specific point in time.
Other than causing Professor Hawking a whole bunch of headaches, I don't see this new observation as doing a whole lot. There may be a way to exploit the technique to generate an animated hologram, though, as you'd have a way of influencing interference patterns with respect to time from a single image, but that's about it.
It's a small world and it smells funny; I'd buy another if it wasn't for the money; Take back what I paid (SoM)
It's too bad more laypeople don't get into quantum physics, string theory, etc. The implicatisons are pretty amazing on both scientific and spiritual levels, and I have chosen to read much of what this science tells us as: The Universe (Multiverse) is One and Many simultaneously, we are all a part of it, and in essence, are all One. Time is an illusion on the ultimate level, as is the notion of our matter and energy being separate from every other element of the universe. Thus, death as we know it does not truly exist, when what you are is a focal point of the neverending Multiverse (God, if you wanna put it that way -- but that's up to you).
Gee... I wonder why they don't teach any of this stuff in the school system, unless you happen to go into phsyics?
I highly recommend The Tao of Physics by Capra (which I'm sure many scientists loathe). Also writings by Nick Herbert are pretty interesting. A lot of the stuff we are finding equations for now is what many indegenous cultures have taught for thousands and thousands of years. They may have communicated the ideas differently, but they strike me as having the same message.
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The techno-mediated cultural conspiracy
http://thewired.blogs.com/teotwawki/
With string theory under your belt, you can be as sloppy as you like.
String theorists are to physicists what physicists are to the rest of the world.