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Physicists Watch Individual Electrons Flow
SG writes "Physicists at the Tokyo Institute of Technology have developed the world's most sensitive ammeter yet. The device allows current to be measured at the attoampere level and is expected to be of use in nanoelectronics, calibration devices, quantum computation and biology."
Here's a picture of the ammeter in action.
For the likes of Intel, this is the hardware equivalent of gdb.
Would it have to change the flow by measuring it? How much by pure quantum "observation" effects?
As a non-phyisics grad (Computer science), I'm wondering.
Ryan Fenton
So now ol' Ben Franklin can finally see which direction electrons really flow!
Just because it can't be explained doesn't mean it isn't true. Science fits into reality... not the other way around.
My question is if I want to measure current (assume an ideal current source) then I will hook it up to this new invention. The mechanism of current in this new measuring device is quantum tunneling. Is there any reason that the current source in question employs the same mechanism. It may still be conventional drift-diffusion with very very low fields (and probably very low mobility). Now when I interface it with this double-quantum device, does the change in mechanism ensures current quantity ? If answer yes, what is the intutive answer. I can understand current continuity when it is drift and diffusion.
It's alright. I'm sure there is no electrical activity in your brain. You're safe. :-)
Before you read any of the article and just say the headline: "Physicists Watch Individual Electrons Flow" did anyone think of a bunch of guys in white lab coats looking down at a table with money in their fists betting on electron races? Because I did... And boy was it disturbing... Gambling physicists can be very rude. (At least the ones in my head are)
Eating the brains of your enemies does not make you smarter. But it's still fun.
Just because it _may not_ be of any use today does not mean that it will always be "useless". The parabola was known to the ancient Greeks but it only saw its first "practical" use in the hands of Galileo Galilei who used it to predict the trajectory of cannon balls.
Two roads diverged in a wood, and I - I took the one less travelled by. (Robert Frost, 1916)
http://www.analogzone.com/tmt_0912.pdf
For an unknow reason, their device automatically falls into sleep mode after having counted too many electrons.
We already know the answer to that. "Wave propagation" and "particle interaction" are redundant expressions; "wave interaction" and "particle propagation" are oxymoronic. "Waves" and "particles" are not entities or properties but rather behaviors - wave propagation is the constant or increasing lack of information about the quantum relative to the observer/instrument/indicator and particle interaction is the creation or transmission of information relative to the observer/instrument/indicator.
Single particle interactions are never in two places at once. The information that originally was one quantum may be distributed across space as it propagates as a wave or distributed across ensembles of different quanta in entangled states, but the interactions (particles) themselves are always strictly local.
"Is life so dear, or peace so sweet, as to be purchased at the price of chains and slavery?" - Patrick Henry
Can't dowse for shit with one of those.
KFG
The big one, I think, will be allowing the SI definition of current to be changed from the present unwieldly method of "an ampere is the steady current that when flowing in straight parallel wires of infinite length and negligible cross section, separated by a distance of one meter in free space, produces a force between the wires of 2 × 10-7 newtons per meter of length", then defining the Coulomb as "the charge delivered by a current of 1 ampere in 1 second".
The new, accurate electron counting capability alows the quantum of electrical charge to become the base unit, as it should be, and then to define current as the number of charges per second.
"Is life so dear, or peace so sweet, as to be purchased at the price of chains and slavery?" - Patrick Henry
You're talking about the double-slit experiment or two-slit experiment consisting of letting light diffract through two slits producing fringes on a screen. These fringes or interference patterns have light and dark regions corresponding to where the light waves have constructively and destructively interfered. The experiment can also be performed with a beam of electrons or atoms, showing similar interference patterns; this is taken as evidence of the "wave-particle duality" predicted by quantum physics. Note, however, that a double-slit experiment can also be performed with water waves in a ripple tank; the explanation of the observed wave phenomena does not require quantum mechanics in any way. The phenomenon is quantum mechanical only when quantum particles - such as atoms, electrons, or photons - manifest as waves. I doubt the machine will be able to distinguish whether one electron goes through one slit and/or vice/versa. Remember, observing the behavior of these particles causes the wave pattern to collapse. They're almost there, but they're very far off at the same time.
Ahh, the wayward electron...
It must have been something you assimilated. . . .
I think that a plausible explanation (or at least one that deserves more research) is the Pilot Wave theory proposed by de Broglie-Bohm. See http://plato.stanford.edu/entries/qm-bohm/ and other numerous sites for a discusion of this proposition. (Disclaimer: I have never been a big fan of the Copenhagen Interpetation.) Nonetheless, I feel that an explanation which obviates the "observer problem" and explains decoherence merits looking at.
I don't trust atoms -- they make up stuff.
You misunderstand what the double slit experiment involves.
In the double slit experiment, the light or particle source that is used is turned down so low that at any given time, there is no more than 1 particle going through the barrier.
This cannot be replicated in a ripple tank. A ripple tank, or any kind of macro scale wave inherently cannot produce the same result as the double slit experiment because it can not be proven that any individual particle is the wave is interfering with itself.
I'm gonna need a spec.
Because you can study the physics of smaller and smaller systems. There are only a few areas that this device will be useful, but researchers are always fighting against noise while trying to increase the sensitivity of their devices.
Up until now the record for smallest current was about 100 attoamps with a dc squid. The great thing about them is that you can detect currents from 100 attoamps (if you're very, very careful) all the way up to milliamps, all in the same device in the same setup.
This new device with coupled quantum dots will only work on the attoamp scale, so is not as versatile, but the years of work that went into designing, fabricating, and measuring this device is astounding.
Think about it, they are measuring individual electrons, they are fighting against a huge number of electrons surrounding their devices, which experience random thermal noise. The thermal noise in the shielding around their device can generate eddy currents of the order of what they are detecting so they had to account for that too, and design special shielding.
Not only that, they have to think about the coupling of the quantum dots. You only want charge transfer from resonant tunneling, if the dots are too strongly coupled to their surroundings the quantum coherence is swamped, the linewidths of the levels being populated would be broadened too much. And if they are not coupled strong enough, you won't get enough resonant tunneling.
Of course there are a lot more considerations, going from concept, design parameters, actual method of fabrication and preparation, detection methods, and noise and data analysis.
All in all it's a great technical achievement to do what they've done.