Is it possible to measure the speed at which quantum tunneling occurs?
553192
speed?\n\nquantum tunneling happens by chance in time, so the word speed doesnt apply here.\n\nBut once it takes place, the tunneling occurs at the speed of light.
772425
As I understand it, electrons don't travel any continuous trajectory the way large objects do.  They basically teleport from one place to another.  When they say it travels every possible trajectory, they mean there's a nonzero probability of finding it in any given place, with the probability decreasing the farther away you look.  However, I think that's still constrained by the speed of light--you won't find it a zillion miles away an instant from now.  For those trajectories, the probability of finding the electron there drops to zero.\n\nSaying an electron travels every possible trajectory is really just one of several interpretations of quantum theory.  The theory only gives us the probabilities of observing certain results; it doesn't explain what the particles actually did to produce those results.
84433
Theoretically, electrons move at the speed of light. To measure accurately a delay of 1 ms would require two wires, each 93 miles long.
364039
depends on the medium they are transmitted through- if current in a wire, light in a vacuum is faster, if electron flow through a vacuum, like a radio signal- nearly same speed with light having a tiny edge.
77099
it would be called superluminal.\n\nyou can read more about it here - \nhttp://en.wikipedia.org/wiki/Faster_than_light
44625
The speed of sound (at sea level) approximately is 340.29 m/s and can be used as a global estimate for the speed of sound for the purposes of this calculation.  That would mean that students measuring such a sound would need to be seperated by 340 meters to measure even a 1 second delay in sound propagation.  Additionally they would need to be able to perfectly synchronize the start of the sound event and the start of stopwatch event.  Making it even worse is the need to react with enough speed to stop the stopwatch upon reciept of the signal without significant reaction delay.\n\nThe experiment would be simply to accomplish with resources to control synchronization and detection equipment, but it would not be a low-budget, high-school type of experiment.
392981
Is the speed at which it travels.
1093639
What meant Indeed ?\n\nIt is not a easy question. This question was originally highlighted by Niels Bohr in the Copenhagen interpretation, where a system stops being a superposition of states and becomes either one or the other when an observation takes place. This makes apparent the fact that the nature of measurement, or observation, is not well defined. In other words we can measure position, but not the velocity or we can measure velocity, but not the position. \n\nI did mention Schrödinger's cat did not I? The Schrödinger's cat paradox suggests that by the act of quantum measurement we are destroying the object of measurement and hopefully not before we obtain one particular property. \nhttp://en.wikipedia.org/wiki/Schr%C3%B6dinger%27s_cat  \n\nSo by ‘measurement’ in QM we mean “In classical physics the mathematical model talks about the things we observe. In QM the mathematical model by itself never produces observations. We must interpret the wave function in order to relate it to experimental observations.” http://www.mtnmath.com/faq/meas-qm-2.html   \n\nI hope that tickles you, but I suspect you knew the answer.
90556
Always exactly the same speed, c = 299 792 458 meters/second, no acceleration or deceleration or anything.\n\nThe *apparent* speed of light through glass is less than c, but that is because the photons (the light) bounce off all the atoms and that slows down the speed through the glass. The speed of light from one atom to the next is exactly c.\n\nAlso, sometimes you will read about experiments where the popular press version says some bunch of light has been made to faster than c, but this is just the phase speed and so isn't quite the same thing. You can't send any information faster than c with this method.\n\nThere is an apparent something that goes faster than light in what is called the EPR-effect, a wierd property of quantum mechanics often misleadingly called "quantum teleportation," but again, no information travels faster than c.\n\nThere are hypothetical particles called tachyons which *always* go faster than light - they can't go slower. But no evidence for these have been found and most physicists think they can't exist.\n\nAs for warp drives and other faster-than-light science fiction type things, that, in my opinion isn't possible. Certainly everything we know about physics and the universe now says it is impossible, and it is unlikely that any future theory will show we are so wrong now that we missed this one. Also if FTL is possible then you can have a sort of time travel, and then cause and effect get ruines and, well, its a mess.\n\nBe glad that c is absolutely the same to all observers in every situation - the universe wouldn't work without it.
1128096
If you want an answer based on the known theories or experiments... they all will fail on the very assumption of something moving at speed greater than speed of light.\n\nBut in principle.... if something like that can be done.. it would be possible if not clearly see.. but record such events.\n\nMicrowave Background Radiation (if you have ever heard off) are the signatures of what must have happened at time of birth of universe i.e. just after big bang.
251335
It can be "explained" with quantum mechanics. If you can find the movies of the lectures given by Richard Feynmen in New Zealand, there are 4 lectures if I am correct, In the first lecture he explains it very well in Laymans terms.\n\nIt takes a fair bit of explanation so I won't attemp to relate it here.
801633
Hi, \n\nThat's too much like real work, but think about it like breaking pool balls in classical, and wave interference with quantum. \n\nHope that helps, \nMatt
363614
Quantum tunnelling ( passage of electrons/atoms through a potential energy barrier and/or other matter .... it's a probability thing ) has been suggested as a possible reason.
531425
Don't understand your question. Did you proof read it? I bet you didn't, did you? \n\nDo you mean 'is quantum theory able to define a quantum of a quantum?'?\n\nIf so, the answer is no. A quantum is by definition the smallest step unit. The smallest unit of energy is h bar, which equals h over 2pi.
661036
Yes. Theoretically, if you try to determine the 'place' of a photon 'exactly' as if it is a particle, you will not be able to detect it's velocity. And when you want to know its 'exact' speed, you will have no idea about where it is, just like a wave.
353533
If you could find a transition between an inverted state and a ground state of 1 joule, you could probably make a laser of that frequency. At this point, hard gamma rays are the limit we have done.
46789
well, to some extent the answer to this question depends largely on the nature of the nanostructure and what its function will be.  in some cases, the tunneling is a problem, but in other cases, the structures are designed specifically to take advantage of tunneling effects.\n\n(i also notice you wrote atomic tunneling - did you mean electron tunneling?  an atom *can* tunnel, theoretically, but because it is a composite object, the probability is extraordinarily low that all of the particles in the atom will tunnel at once.  \n\nalso, the particles in the nucleus are very small, very light, and very tightly bound.. as such their tunneling lengths are much smaller than the size of the atom itself.  so while it is possible that the nucleus could be involved in tunneling, it is very unlikely on scales larger than a femtometer, which is much smaller than even a single atom.  so, i will assume you mean electron tunneling, which is what most people talk about.)\n\nanyway, one problem that springs to mind is becoming more and more important in the semiconductor industry.  you may have heard of moore's law, which is an observation that over the lifetime of the integrated circuit industry, the "feature size" or structure size has been halved approximately every 18 months.  this means that transistors and wires shrink, and more and more components get squeezed together on a silicon chip.\n\ntunneling is a problem in this situation since it sets an ultimate limit on how small these features can get.  intel for example is ramping up to create processors with a 45-nanometer feature size by 2007.  these things certainly qualify as nanostructures.\n\nhowever, once you get under about 10nm or so, the wires and so on will be so closely spaced that electrons will tunnel from one to the other; this could turn a 0 into a 1, which would be a Bad Thing.  a way around this is to design circuits that are so-called "fault-tolerant" but this requires more hardware - which will only buy you a little bit of time, since more hardware offsets the smaller-hardware gain.  so this is a fundamental limit to standard circuits imposed by tunneling.\n\non the other hand, lots of nanostructures are currently being researched that take advantage of tunneling effects.  there is a whole sub-field of materials/physical science that can be called "single-electron electronics".  this is where one electron is used to represent a bit, rather than the thousands or millions used in normal electronics.\n\nthese electronics are typically made out of clusters of atoms called "quantum dots" and a few molecules.  at this size, tunneling effects are the primary source of the functionality of these devices!  people are working on single-electron transistors where an electron tunneling across a nanometer-sized barrier performs the "switching" that makes a transistor useful.  you could google the phrase "coulomb staircase" to see instances of this phenomenon.  \n\nthere is a lot of active research in this area - for example, here is the page of a guy in my department, who is working on using gold nanoparticles as the tunneling barrier between two long polymer "wires":  http://www.chem.utoronto.ca/staff/DHIRANI/research.htm\n\nhowever, at this point the state of the art is pretty primitive - certain building blocks like transistors and single logic gates have been made, but it's difficult to make them into larger functional circuits because they're so damned small.\n\nactually, now that i've written all this i see that you asked about the *creation* of nanostructures.  there are lots of different ways of creating nanostructured materials.  some involve self-assembly, where molecules arrange themselves into nanometer-sized structures because that structure is energetically favorable.  other ways include blasting away at some bulk material with a tightly focused beam (see focused-ion-beam (FIB) etchin