in the quantum dot, richard turton asks us to:
suppose that we produce an array of quantum dots using a grid of electrodes which divides the surface into squares about a tenth of a micron across. a quick calculation shows that we could place 10 billion of these on an area of one square centimeter. if each one serves as a resonant tunneling transistor, performing the function of several conventional transistors, such a structure should have a capability far in excess of the most powerful present-day supercomputer, and all of this on a single chip!
ee designers seem to be at odds over the question of molecular electronics. many chip designers believe that alternate computing technologies such as quantum dots may eventually supplant conventional silicon. other chip designers are skeptical, and ask “when we figure out how big a molecule has to be to be an effective transistor, how much smaller is it than a semiconductor transistor?” in order to work effectively at room temperature quantum dots might need to be 10 nanometers in size. if we can fabricate 10 nanometer structures, why not simply fabricate 10 nm silicon transistors, which can be created through conventional means? quantum dots would have compelling advantages over conventional transistors: they wouldn't leak, and they wouldn't need the complex wiring schemes that conventional microchips require. but would these advantages justify the enormous expense of developing a new technological infrastructure? intel ceo andy grove has stated that disruptive technologies need to be an order of magnitude better than conventional technologies in order to justify the expense and difficulty of mass-producing a new technology. silicon mosfet technology seems safe for the next decade, but what about in the long run? titanium is in many respects superior to steel, but for most tasks steel is used because it is so much cheaper. will alternate technologies (such as quantum dots) eventually replace conventional silicon transistors entirely, or will these “post cmos” technologies only be used in situations where silicon isn't adequate? i am interested to hear readers' views on this subject.
user comments 27 comment(s)
|i guess… (9:14am est wed mar 12 2003)
quantum is the future of all microsystems! it is much more powerful and less pollutant. it is also renewable! minus: as usual, the price will be a little higher at first, but it will decrease as the units become more common and popular. all i can say is that this is a really promising technology, and it will alter all of the mankind! – by sexwithmi
|quantum dots (9:16am est wed mar 12 2003)
what good is a 10-billion-transistor processor if it dissipates 1000 watts? how much power will these monsters use? – by zero db
|power (9:24am est wed mar 12 2003)
well from the look of it i would guess they would disipate much less heat an order of magnitude less i would guess as they don't leak current, like the current silicon transistors and don't need the complicated wiring of current silicon transisitors. – by pskyboy
|temperature (9:46am est wed mar 12 2003)
for quantum dots to work at room temperature you need dimensions order of 3,5 nm or less. but molecular electronics works at these dimensions too. right choice? see:
– by adi porobic
|i've been having to do research on the subject…. (10:50am est wed mar 12 2003)
and from what i have been reading, quantum computing would begin with quantum transisters of some kind. the benefits of quantum computing are large for applicates of security and research because of the unique properties of qubits. they have yet to discover benefits for gamers, but i am sure they are out there. when they do so, i can't help but think, why shouldn't they simply convert to quantum dots.
i mean, different types of alogerithms would allow for better computing. and some say quantum computing is the way to understanding what we have yet to understand. since we are all curious creatures, it would seem counter productive to not move on to some kind of quantum technology. – by cwtrex
|quantumness! (11:02am est wed mar 12 2003)
well this whole nlurb takes me back to the posts about the concerns that moore's law is starting to look as if it will come to an end. we still have quite a bit of evoloution/technological advances before moore's law comes to an exponential end. anyway back to the post. new technology that is better than current, almost always currently replaces the current technology, prices are higher on the new technology but they do lower. i mean look how flat screen tv's went from $50,000, to $3,000 42 inch plasma screens. and this kind of technological advance is far outranking when comparing plasma to regular old tv's. titanium isn't a very good example to use in my opinion. titanium is not much of a business driven material, so prices aren't going to deflate. if titanium was used to make say a car last 100 years, then you would see a battle for this material, cheaper ways to make it, sell it, etc prices drop dramtically. this kind of technology will be used everywhere. sure it may start out only being used as super computers, military, etc. when the public gets ahold of this though it becomes a consumer resource, they find better, faster, cheaper ways to make it, sell it, plus competition. not to mention all the other companies that would eat this up in making new advanced software that would run on this new technology. pretty soon everyone wants the technology, needs it to play their new 3d games and run their windows 2008 or whatever:) – by crevin
|crevin (11:44am est wed mar 12 2003)
the later part of that is only for the number of transisters alone. noone (or at least in my research anyway) … has figured out any major benefits that would make quantum parts a dramatic improvement in some new 3d game or to run windows 3000.
this may come with more research, however. but your current point is a bit in the water on this subject when dealing with quantum mechanics. – by cwtrex
|will they replace silicon (11:54am est wed mar 12 2003)
yes – by averyboy
|finally!!! (12:45pm est wed mar 12 2003)
i will be happy when they can have a world like rifts(palladium universe) on a single system.
1600×1200, full detail – cinema 3d
that is what quantum computing promises. so much power that we never have to go back to reality. forget hyper threading, you will have super power on one chip. reality on reality!!
– by gamer salivating!!!!
|doing it right (1:22pm est wed mar 12 2003)
it is my belief that in order for completely new technologies to be effective, totally new systems must be created to take advantage of their strengths. if quantum chip designers use silicon theories in their systems, they will be trying to emmulate silicon, which it isn't.
only by allowing quantum chips to operate as quantum chips, and not silicon chips, will they be able to surpass silicon technology. it's like making a 64bit chip run 8 bit code, you'll only see the full potential when you update everything and run 64 bit code.
for some reason it always takes people a couple of hardware generations to figure this out. – by crashless
|divergence (2:05pm est wed mar 12 2003)
in terms of highest total theoretical performance, quantum dots are currently the best. they will probably be the core technology used for future ultra high speed and serial type computations.
in terms of best theoretical cost to performance ratio, massive arrays of polymer based logic is currently the best. it will probably be used for most mainstream consumer electronics eventually.
|price (4:18pm est wed mar 12 2003)
transistors were around in the 1940s, but the price was so high only the military could use them. by the mid 50s they were making expensive but small and low power radios out of them.
when they were first produced the argument was that they would be expensive to replace, unlike tubes which could be changed faster than a light bulb. the counterargument (which was not widely believed) was that they don't burn out and at any rate they would soon cost less than a penny apiece.
seems like the same arguments against quantum transistors.
dig me up and wake me when these things are mainstream. – by /sm
|crevin (4:23pm est wed mar 12 2003)
“if titanium was used to make say a car last 100 years, then you would see a battle for this material”
nope, they wouldn't do it. they only started making cars last 15-20 years instead of 5 because the costs of a new car rose too high, and ppl needed to keep them longer in order to pay off the incredibly huge bill. in 1963 a corvette was $3,000.
in the 1880s they were warrenting steam locomotives for 200 years. seems to me that a hundred year car would be trivial with today's technology.
a stereo reciever that would effectively last forever could be built easily today, if all the parts were soldered instead of wire wrapped and the potentiometers and switches were replaced by solid state touch switches. but then they could only sell you one. – by /sm
|crashless (4:25pm est wed mar 12 2003)
“it is my belief that in order for completely new technologies to be effective, totally new systems must be created to take advantage of their strengths.”
erm, how are transistors used any differently than vacuum tubes? – by /sm
|/sm (4:36pm est wed mar 12 2003)
they aren't. someone wanted to miniturize the tube, so they found a way to do that in silicon. i'm no technical theorist, but what if people are looking at silicon all wrong?
what if silicon could be used under pressure situations to send signals without etched paths? i'm merely suggesting a theoretical possibility. i'm not suggesting that transistors are an ineffective use of silicon, but i am suggesting there may be more efficient uses of the medium. – by crashless
|/sm (4:36pm est wed mar 12 2003)
with quantum technology crashless would be right. it's been a block to any real thinking in quantum computing that you have to actually think differently because of the way quantum mechanics works.
but of course with the move from vacuum tubes and transistors, you are right.
what i'm interested in is seeing if we can gain the ability to transport ourselves to anywhere in the world at any given time with quantum mechanics. they say it's possible, but is it really ? – by cwtrex
|where's the reliability? (12:48am est thu mar 13 2003)
the first alpha particle that comes along and there goes your qubit. in servers you get single bit errors weekly, so how the heck are these ever going to be reliable? at least with current semiconductor technology you have 100's, even 1000's of atoms in each cell and the odd occaisonal hot electron doesn't kill the whole transistor.
– by yetanothergeekguy
|error correction (2:37am est thu mar 13 2003)
quantum dot pcs, not in the near future
the amount of error correction needed with quantum computers kills any advantage over silicon for all but the highest levels of computing, things that just can not be done practically with silicon. these specailist processors will not have applications for average folks for a long time to come.
i think optical processing is the future, but only as the core. i'm middle age and expect this in my lifetime.
silicon will always have a role. i would not be suprised if optical engineers announce they could do the same type algorithms as qbits, but using a simpler and more reliable holographic system. seems intuitive.
|dozens of fallacies… (5:11am est thu mar 13 2003)
well, if i must:
quantum dots are defined as “small islands of metal insulated from the surrounding conductors… which can contain zero to a few hundred individual electrons.”
 they do leak. a kind of specialized capacitor essentially, they're as prone to leakage as any other capacitor. worse, because their dielectric is much thinner, they tend to gain and lose electrons in bunches (well, all caps do)… its just that when you own 4 electrons, a 'bunch of 3' reduces your charge to near nuthin.
 quantum dots don't 'compute' using q-bits. a horribly esoteric topic, in essence q-bits are quantum spin-states that support a virtually infinite [theoretical] number of overlapping states per quantum wavefunction particle. this is not a quantum dot!
 qdots are usually floating gates above conventional mos transistors. their state is determined by electrostatic charge/discharge forces.
 qdots are relatively slow. like dram, they need to be carefuly charged, carefully 'leaked'.
 qdots don't conserve charge transfer when working in cellular automata mode. in other words, they're lossy. losses require amplification. that requires power & time. together amps, dots, power, time & losses mean heat, wasted space, complex surface structures, …
so i don't see a great gain. to me, qdots are just a glorfied version of “dram cells that can compute”.
i see far more lucre being wrought from the spintronics industry. cmr and its kin, being essentially the first significant solid state technology that is both quantum-efficient and independent of silicon/iv or iii:v semiconduction is key.
– by goatguy
|cwtrex (9:01am est thu mar 13 2003)
“what i'm interested in is seeing if we can gain the ability to transport ourselves to anywhere in the world at any given time with quantum mechanics. they say it's possible, but is it really ?”
ten years ago i'd have said no fraggin way. now that they have actually teleported electrons or photons or something a few feet, i'm starting to wonder if they might actually do it some day. – by /sm
|goatguy (9:06am est thu mar 13 2003)
“…q-bits are quantum spin-states that support a virtually infinite [theoretical] number of overlapping states per quantum wavefunction particle.”
hmm… this sounds like a truly analog transistor could be made out of them? if so we could finally replace vacuum tubes completely, or even bring back analog computers.
? what say? – by /sm
|high jinks! (1:09pm est thu mar 13 2003)
great comedy, /sm/.
even today, all transistors are essentially analog devices. they have always been used in 'saturation mode' in cmos type structures. digital gains its great power over analogue by being virtually insensitive to the wisps of noise that plague analog designs.
nothing “wrong per se” about an analog computer… but the results take awhile to settle down, and rather like the old fashioned slide-rule, don't have more than a couple of digits of precision.
in fact, the limitation of true quantum computing is that the nearly infinite number of states cannot be discriminated due both to thermal decoherence and heisenberg's uncertainty principle. as one quantum researcher said to the other, “eureka! we've found the answer!!!” … “and what is it?” … “well, we lost it before it came out, but we know it was there!”
– by goatguy
|goatguy (4:08pm est thu mar 13 2003)
you appear to be way more knowledgeable than i, and are probably an electrical engineer so maybe you can set me straight, i may have been laboring under a misconception for the last 3 decades.
the argument against transistors (vs tubes) was that tubes are amplifiers, while transistors are just very fast switches- that a transistor's “analog” output was a result of its switching on and off very fast, sort of like you “dim” an lcd by switching it on and off w/ shorter “offs” and longer “ons”. when fets amd mosfets came out the argument kind of went away untill recently, when musicians began buying tube amps again.
so, is a transistor truly analog, or is it a switch? if it is truly analog, how does it work?
btw, you're a patient guy to put up w/ my ignorant questions – by /sm
|quantum mind (4:16pm est thu mar 13 2003)
just an interesting side topic, there are theories that the human brain is infact a quantum computing device. the theory i prefer best deals with how our neural transmitters are shaped. here's the link:
enjoy – by diesson
|a few comments…. (4:55pm est thu mar 13 2003)
quantum dots are structures that are designed to constrain *energy levels* to discrete levels. the number of electrons is only incidental. many people have jumped on the bandwagon with quantum dots but are really only useing them as nanocapacitors, as goatguy pointed out. that sort of use doesn't exploit qd's real benefit (multistable states). it's like useing a transistor in analog mode instead of digital.
the fundametal problem with single quanta systems, photonics and spintronics included, is that certainty requires an infinite ammount of energy. all quanta have non-zero probababilities of randomly switching states at anything less. this means you need non-trivial error correction at the most basic level in addition to powerful cooling, rf shielding, magnetic shielding and physical damping. and your quantum coherence will still decay in a very short period of time and even quicker if you let it interact with anything. if you think dram that can't maintain it's value is annoying and wasteful, immagine trying to design anything non-trivial with logic that doesnt't maintain it's properties. the vast majority of any such device will be support systems an not useful logic. incidently, it would be extremely io limited. :)
multistable molecules by constrast, are comprised of combinations that already average out undesirable quantum uncertainty. they already exist, but are not compatible with current mass fabrication techniques (except lcds). by all measures, they're a more realistic technology for general applications than photonics or spintronics. they require no power to maintain state, only to change so there is much less power used and much less heat generated. since there are no current loops, there is almost no rf effects. they are self contained and don't require sophisticated lab environments.
|we still have not yet discovered it. (6:47pm est thu mar 13 2003)
in order to fully understand quantum physics, and how to control them, we must first understand the “dark matter”, that constitutes 95% of the universe mass.
the dark matter occasionally collides with atoms (protons or neutrons), creating unpredictable vibrations that is just being vaguely discovered today. it is probably what causes gravity in the first place. over 500 billion dark matter particles (not photons or phonons, smaller!) travel through one square meter per second, due to earth's movement through space. the dark matter is like the “filling” of the universe, that generally resides in large gas-like clouds around galaxies. we are just at the brink of eventually discovering this ultimate mystery that baffled albert einstein all the way to death. – by affez pow
|speed limit (9:13pm est tue apr 05 2005)
we may have already hit the speed limit of current processors. i have seen a couple of machines slow down as they age, indicating perhaps a breakdown in the silicon. – by mec