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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."
If you read this is simply a device that channels electrons into a single file channel then measures the movement through the channel. Akin to putting a dam in water then putting a very small pipe in the dam and putting a meter on that. What you are ultimatly changing is the amount of electrons that get through, so I'm guessing to measure a current of any size you would have to have millions or more of these???
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)
A ghost detector? Amazing new technology comes around and all you can think of is a ghost detector?? Sheesh...
:)
dowsers already do that just fine.
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Except that charge is what's moving, not necessarily 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
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
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.