In the palmy days of the BBC Micro, a young lady (rather like SG, I suppose) wrote to a magazine that she wrote such a program in BBC Basic, but it took 90 minutes to run. So I tried, and mine ran in about 3.5 seconds (on a 4 MHz 6502). The fastest reported took 250 ms!
-- Regards, John Woodgate, OOO - Own Opinions Only. There are two sides to every question, except 'What is a Moebius strip?' http://www.jmwa.demon.co.uk Also see http://www.isce.org.uk
That doesn't make sense. Some go through one and others go through the other and some don't go through at all. How can ONE photon go through TWO slits at the same time? Pauli's exclusion principle says that no two can be in the same state, and one condition of state is position, at the same time. So, ONE should not be able to have TWO positions at one time, either.
Or... let me guess, I'm mistaken again?
I read in sci.electronics.design that ~~SciGirl~~ wrote (in ) about 'Wormhole theory', on Thu, 31 Mar 2005:
Photons are bosons, but the Pauli principle applies only to fermions. Quote from:
"It turned out that the exclusion principle applies to particles with half-integral spin, e.g. electrons and protons. If these particles are described quantum statistically, then the so-called Fermi-Dirac statistics are employed. Such particles are known as fermions. On the other hand, particles with integral spin, e.g. photons, do not obey the exclusion principle and follow Bose-Einstein statistics. Such particles are known as bosons."
But this is not very relevant to the two-slit experiment.
Yes. But don't be put off. It's one of the most initially astonishing demonstrations of quantum effects in action. Google gives a lot of hits, but this one seems to be pretty lucid:
-- Regards, John Woodgate, OOO - Own Opinions Only. There are two sides to every question, except 'What is a Moebius strip?' http://www.jmwa.demon.co.uk Also see http://www.isce.org.uk
In the US, engineers are almost always judged by a 2 to 3 hour interview, often a group interview. I hate those. I had an interview at UC Berkeley recently, where I was 'gang-interviewd' by about 15 phd candidates (1/2 my age), in groups of 5 or 6. I've always thought a 10 minute interview to weed out the liars, followed by a 2 week paid trial period would be far more appropriate, and much more accurate. Termination at the end of the trial would be manditory, followed by a 2 week cooling down period. After that, a rational mutual decision could be reached.
Usually, the basic idea is that they want to make sure you know the simple tricks. Often, however, the questions are designed to put you under pressure, just to see what happens. The guys at cisco used to really love to brutalize folks during interviews. They would brag about it afterwards, describing how some poor guy had folded under the pressure.
When I graduated from college, I had a microsoft guy ask me how to build a doubly linked list with a single pointer word per list element. Happily, a CS professor has clued a group of us in to the XOR trick a few weeks before. Store addr(L) xor addr(R) in each element. Then if you have pointers to two sequential elements in the chain, you can go either direction. It's a neat trick, but after nearly 25 years of writing software ranging from user interfaces to communications protocols to operating systems, I have yet to use it for anything.
--
Regards,
Robert Monsen
"Your Highness, I have no need of this hypothesis."
- Pierre Laplace (1749-1827), to Napoleon,
on why his works on celestial mechanics make no mention of God.
Such is the way of all cute tricks ;-)
...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona Voice:(480)460-2350 | |
| E-mail Address at Website Fax:(480)460-2142 | Brass Rat |
| http://www.analog-innovations.com | 1962 |
I love to cook with wine. Sometimes I even put it in the food.
No.
Oh dear...we went all over this a while back. This two places at once nonsense is nothing more then an ad-hoc metaphysical add on to QM. Its not required in the slightest. Indeed, it is specifically excluded by the postulates of QM, to wit:
The only possible measured value to result from a quantum mechanical observable A is one of its eigenvalues.
It can only have one value, not two. What it does prior to measurement is anybody's guess.
Kevin Aylward snipped-for-privacy@anasoft.co.uk
I read in sci.electronics.design that Kevin Aylward wrote (in ) about 'Wormhole theory', on Fri, 1 Apr 2005:
Yes, Kevin, but SciGirl is just starting out. She's going to read a lot more of the 'conventional' descriptions of the experiment and its results than descriptions based on your more up-to-date explanation.
Besides, by the time she is ready for your explanation, it may well, in its turn, have been replaced by something even newer.
-- Regards, John Woodgate, OOO - Own Opinions Only. There are two sides to every question, except 'What is a Moebius strip?' http://www.jmwa.demon.co.uk Also see http://www.isce.org.uk
No. With all due respect to John, he is mistaken. Nothing in QM demands that particles go through two slits at once, i.e. can be in two positions at once. Indeed, QM specifically prohibits any such measurement from occurring.
The idea of two places at once is a ad-hoc additional interpretation to QM that quite a few use as a bit of hand waving. Have a look here
What people do is fluff one argument with another one, and say that the later argument has relevance to the first. It don't. A typical example of such erroneous logic is here:
Fig. A and its experiment proves conclusively that photons are not two places at once for that arrangement. To waffle around this Fig. B and Fig. C are used with an argument to *infer* what *might* happen if the detectors were not there. Well, this is completely irrelevant. Such a set-up would be a different set-up, and hence completely meaningless to the question posed for the first set-up.
Indeed, one other *interpretation*, Bohemian Mechanics, can actually show trajectories that particles can take,
Most of what one reads on QM, is all stuff dreamed up at the orignal inception of QM. Many of those ideas have been replaced, many of them are simply wrong. Unfortunately, layman's QM just hasn't kept place with today's reality.
e.g (ref. above)
Dr Willem M. de Muynck, Department of Applied Physics, Eindhoven University of Technology:
"A related consequence of a realist version of an individual-particle interpretation of the quantum mechanical state vector is that a microscopic object must split if the state vector does so. For instance, in neutron interference experiments of the type considered in Publ. 27 this would imply that a neutron traversing a neutron interferometer does so while being split into two halves, each of which taking a different path. Since this is in disagreement with all empirical data (strongly suggesting that each neutron follows either one path or the other) a realist individual-particle interpretation of the quantum mechanical state vector is unattractive (as is the "suspended animation" interpretation of the Schrödinger's cat state referred to above). It is quite remarkable that nevertheless this interpretation is widely entertained. This may be due to the popular idea of particle-wave duality, having been developed in the Copenhagen interpretation during the early stages of the development of quantum mechanics, but being obsolete by now"
People just haven't moved on. They are still stuck in the 1920's
Kevin Aylward snipped-for-privacy@anasoft.co.uk
I read in sci.electronics.design that Kevin Aylward wrote (in ) about 'Wormhole theory', on Fri, 1 Apr 2005:
See my other post. You are likely to confuse SciGirl rather than enlighten. In any case, my original statement was a JOKE about particles 'thinking'.
-- Regards, John Woodgate, OOO - Own Opinions Only. There are two sides to every question, except 'What is a Moebius strip?' http://www.jmwa.demon.co.uk Also see http://www.isce.org.uk
Wait a sec - are you saying I was actually right for once? That one particle can't be in two places simultaneously?
Well, here's another reason - simultaneous events are impossible. So even if one photon could be in two places, it couldn't be at the same time... unless maybe if you go by the QM definition of "Event" (from the Elementary Particle Physics Glossary)
I read in sci.electronics.design that ~~SciGirl~~ wrote (in ) about 'Wormhole theory', on Sat, 2 Apr 2005:
Where did you get that idea?
-- Regards, John Woodgate, OOO - Own Opinions Only. There are two sides to every question, except 'What is a Moebius strip?' http://www.jmwa.demon.co.uk Also see http://www.isce.org.uk
Yep.
At some future date, in principle, there might well be a *new* theory that redefines what a particle is and has it existing spread out in space, but this would have absolute *nothing* to do with current quantum mechanics, or definitions. By far the majority, e.g do a web scan, are completely clueless on what QM actually says. QM is a mathematical description of measurements. It simply doesn't care about all the ad-hoc waffle that many use to try and "explain" the measurements.
Fundamentally, we can *only* "explain" things in terms of what we already know. Everything has to be referred to some other existing ideas. i.e explanations are all *relative*, in principle. Sooner or later things pop up that can not be explained in terms of what we already know, so we simple have to accept those things as a new principle. If one doesn't do this, one is always going to end up with nonsense in trying to explain these something's that can't be reduced to existing axioms, to wit, a particle in two places at once is inherently contradictory.
There is no known, accepted, way to explain QM in classical terms, that's all there is too it.
Kevin Aylward snipped-for-privacy@anasoft.co.uk
When dealing with KA and his world-view, there is no way of distinguishing one from the other.
If you're worried about a particle going through two slits simultaneously, think about a wave going throuth two gaps in the sea wall.
Cheers! Rich
Who, exactly, told you this?
Thanks, Rich
...and then think about the molecules that make up the water.
-- Keith
Indeed. The wave is just a macroscopic approximation to the statistics of particle motion. What do you think a "water wave" is dude? Its properties are quite well explained by the statistics of classical particles. There is nothing *physical* in a water wave that goes through both slits and once. Dah...
Look, as I have said many times, there was a lot of waffle going on when QM was first invented. A lot of that waffle was wrong. Sure, there might be ideas that go against what a closed mind mind not be able to see, but this aint one of them.
Most simply don't understand the real subtlety of what QM is all about. Its trivially obvious that the science greats of the past fully understood that, e.g. water waves were due to the combined effect of classical particles, and that a classical treatment completely accounted for, e.g. diffraction patterns. There also realised that such explanations failed for quantum particles. QM is much more deep.
Kevin Aylward snipped-for-privacy@anasoft.co.uk
Guess what? I finally got limits!!! (studying from Calculus For The Utterly Confused). And I started with derivatives. It's like when I was trying to understand relativity back in October, I thought about it for a long time and then it randomly all of a sudden made sense.
If it randomly made sense it was QM, not relativity.
-- Keith
I knew you could do it! That shows you can do anything in the sciences, arts or humanities that you put your mind to.
ElectronDepot website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.