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Optical Computer Made From Frozen Light
neutron_p writes "Scientists at Harvard University have shown how ultra-cold atoms can be used to freeze and control light to form the "core" - or central processing unit - of an optical computer. Optical computers would transport information ten times faster than traditional electronic devices, smashing the intrinsic speed limit of silicon technology. This new research could be a major breakthrough in the quest to create super-fast computers that use light instead of electrons to process information. Professor Lene Hau is one of the world's foremost authorities on "slow light". Her research group became famous for slowing down light, which normally travels at 186,000 miles per second, to less than the speed of a bicycle."
Where do I get one of these? No, I want it now
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Most of the positive fanatics write lots of papers; those who think it's not going anywhere (like me) don't. There are sound physical reasons to be skeptical, in my mind:
1) Wavelengths are too big: 1 micron is now a large number, and optics doesn't work much smaller than this.
2) There are no good nonlinearities. Anyone can make a linear OR gate optically, but to function as an effective digital technology you need nonlinearity and level restoration. This is missing in pure optical systems, except at very high power levels. The high power levels imply low density. There are some optical gates which process data in "femtoseconds," but ask them how long it takes to get to the next gate. Maybe someday someone will invent a great, low power, fast, optically nonlinear material. Don't invest in it yet.
3) The serious workers are now mostly working in combined electronic/optical modes. The speeds here are limited by the gate speeds of the electronics, just like normal computers. You have to then ask if optics is a good (cost effective, space efficient, low power...) replacement for wire. Ultimately, the answer is probably yes, but there's an awful lot of work to do before that's true (for the distances of a few centimeters in high density computers, that is).
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BTW, for those interested, here's a direct link to the "Light at Bicycle Speed ... and Slower Yet!" presentation - I was travelling about that speed in
my coldest car during a Colorado snowstorm.
e=mc^2 except where c is like slower and fuck, headache.
Imagine trying to harness today's 3GHz CPUs with 1930s lab bench equipment. Digital electronics could have seemed another universe, out of reach in a universe of alternate physics "beyond radio". If photonic computation is within reach at artifically lowered speeds, we might be just about to cross the watershed, like going from transistor to ENIAC.
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Her research group became famous for slowing down light, which normally travels at 186,000 miles per second, to less than the speed of a bicycle."
Ah, so she worked on IE.
became famous for slowing down light, which normally travels at 186,000 miles per second, to less than the speed of a bicycle.
ah yes, the Speed of a Bicycle (SoaB) metric for slow light.
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The best thing about frozen light is that you can put it in your freezer, so that when there's a blackout, it will thaw and then you'll have light.
>to less than the speed of a bicycle.
So is that
1) A Bicycle with a jet engine strapped to it?
2) A Bicycle going up a hill with an 80 year old man on it?
3) A Bicycle being dropped off a building/cliff
4) A Bicycle being raced?
5) other?
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And this means absolutely nothing to the non-supercomputer world. Light doesn't slow itself down for free. Freezing light for this proccess likely takes the expenditure equal to the GDP of a small country. At best, in the next 50 years there will be 2 frozen light optiocal supercomputers
Free MacMini
I propose that "speed of a bicycle" be adopted as the standard measure of velocity in technical articles. Units already included in the standard are "Libraries of Congress" for data storage requirements and "Size of a Volkswagon" for physical size measurements.
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Imagine a Beowolf Cluster of bicycles!
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...the light freezes you!
Will it at least make and keep my vodka cold, comrade?
Now all we need is Advanced Military Algoritms and Pre-Sentient Algorithms until we achieve Fusion Power and our units become twice as strong as our enemy's units.
Intellectual Integrity and Cyberethics may pose a problem however.
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Obviously it's not simply a temperature thing, since most of space is absolute zero, and I can see stars and suns and stuff. So it's not freezing light as in freezing water.
So how exactly do you stop photons from moving? How does this affect relativity (e=mc^2)? How does this affect our perception of the universe - ie; if the light from the star that we think is 10,000 light years away is only moving 20mph or so, it could really be millions of light years away?
Does like, time slow down? My heads spinning. Freeze sounds like the wrong word.
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The speed of light is _only_ 186,000 mi/sec when traveling through a vacuum. Light travels at slower speeds through all other mediums (i.e. earth's atmosphere, glass, a super-cooled diamond, etc)
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While this may not work (and I emphasize may, isn't it just a wee bit early to pronounce it impossible, implausible, or impractical?
Imagine a Beowolf Cluster of bicycles!
Don't they already do something like that in France?!
From Wikipedia: 'In a sense, any light travelling through a medium other than a vacuum travels below c as a result of refraction. However, certain materials have an exceptionally high refractive index: in particular, the optical density of a Bose-Einstein condensate can be very high. In 1999, a team of scientists led by Lene Hau were able to slow the speed of a light beam to about 17 metres per second, and, in 2001, they were able to momentarily stop a beam.' Slowing light down is nothing new, it happens every time light travels through a medium other than the vacuum of space. Atmosphere, glass window, diamond, etc. It just so happens that we can now create in a laboratory these BEC's, a so-called "superfluid" which is basically a substance cooled to the point where nearly every atom collapses to the lowest quantum state (like, close to absolute zero). This gives it some interesting properties, like zero viscosity and an extremely high optical density. Hope that helps.
The title of this post clearly reads:
Science: Optical Computer Made From Frozen Light
We don't even have a diagram for a logic gate (or at least none are presented in the article) just some supposition in the article that such a thing could be used as a component. As for the 10x faster, where the hell did this number come from? Even if Moore's Law is slowing down (don't nit pick about it be about the number of components on a chip) it will make this "smashing" 10x advantage moot. Perhaps they refer to the speed of light in free space as opposed to signal speed copper. But even this doesn't make sense because signal speed in copper is about c/3.
What really maters is how fast a gate can be made to switch, how easy it is to fabricate enough of them to do something useful, and how close you can pack them together. Until someone can put down on paper the diagram of how this thing would work it is pointless to posit that it would be 10x faster.
Usually for these Pie-in-the-Sky type hype offerings it is common to claim 100x or 1000x or 1,000,000x times.
That BSEs might be used someday as parts in a Quantum computer would be a completely different thing, and those calculations that could be done quantumly would be trillions of times faster, but only for very specific algorithms. This article is not talking about that possibility, but classical computing and I think they have a lot of work to do just to demonstrate a single working component. Let alone claim BSE computers are here or just around the corner.
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2)Really weird phyics like this doesn't start happening until things get really cold. Think tenths or hundredths of a degree above absolute zero. Of course, since energy and temperature are related concepts, at absolute zero, there is no energy, and nothing moves.
3)Relativity is still in effect. In fact it makes a lot of sense here. Less temperature = less energy (e). the speed of light (c) decreases at the same rate as the square root of e. At asbolute zero, e=0 c=0 m=infinity. Time has no meaning to light. Time only slows down/speeds up when your velocity changes with respect to the speed of light. If you were in the supercooled state, time would in fact slow down. The formula for time dialation is here: t'=t(1-(v^2/c^2))^1/2
4) At 1 Kelvin (still colder than space) everything works normally.
5)At ultracold tempearture, Einstein predicted that really funky things would happen. Matter as we think of it tends to break down. It's called the Bose-Einstein condensate.
Free MacMini
Does this mean we can actually make phasers that produce slow photons so we can have cool special effects in real life like Star Wars and Star Trek? Then our super heros can dodge lasers.
I am sure this will be the next product on Think Geek.
D.O.U.O.S.V.A.V.V.M.
6) A bicycle hurled through space at nearly the speed of light?
There again she could be showing us smoke and mirrors. This is light after all. I'm still on the skeptical side.
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Real empty space (if such a thing exists) doesn't have a temperature. Temperature is about how much random kinetic energy something has, and nothing has no energy. (Actually wrong, because of virtual particles and the like, but let's just ignore this for now.)
To freeze light, you reduce the temperature of the medium it travels in. When this gets really, really cold, because of quantum uncertainty, the whole lot stops acting like normal atoms at all, but as a single, big ball of stuff, following a set of mathematical laws known as Bose-Einstein statistics.
A quick digression. How does light travel through the air? Photons and electromagnetic waves are only part of the action. Almost inevitably, a photon hits an atom of air in between. When this happens, it gets absorbed as energy, and this energy gets re-emitted as another photon. Due to the laws of physics, the probabilities are that the emmitted photon is like the original photon. So, measuring from the large scale, light seems to have been slowed down.
My understanding is that this is the same when you send light into the BEC, only that the entire BEC acts like an atom. Freezing light then, is to stop the BEC from re-emitting indefinitely, and just store the properties of the photon.
This has no effects on relativity. And it shouldn't affect our perception of the universe, because BECs are very fragile, and so probably rare.
Einstein showed there is no o bjective measure of speed. Of course, if a bicycle were to travel at the speed of light, it would be very heavy and very long, but, if you were the one riding it, you wouldn't notice...
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I'm going to have to disagree with other repliers on this one. In much of physics (such as relativity and particle physics) it is stated that nothing can travel faster than c, and that light *always* travels at c (never faster or slower). Then in optics you're told that the speed of light depends on the material the light is travelling in. Confusion is understandable.
If you want a picture of what's really going on, think of it this way: *photons* (the fundamental particles of light) always travel at the speed of light, c, as measured by any observer (like relativity says!). However, in optics, when we talk about "light" we don't usually mean individual photons, we mean a massive collection of them, and thus things change a bit. In vacuum, a light beam will travel at exactly c since all the photons travel at c. In a material, however, the photons are continually scattered by the atoms that make it up. These countless scattering events (which are essentially absorption and re-emission events) interfere and generate the final light-beam that we macroscopically observe. The interaction between the photons and the electron clouds in the material lead to time lags, if you will... so that the net macroscopic velocity appears reduced (even though, in principle, the photons travelling from one atom to the next were going at c).
There are experiments where light is "slowed" or "stopped" or even moved backward... and some where light even travels "faster than light." But what is travelling at these speeds is the emergent phenomenon (the envelope of the photon interference pattern), not the individual photons that make it up. Thus, even if the envelope of a photon wave pattern is travelling faster than c (i.e.: the calculated group velocity is >c), you still can't send a signal faster than c. The "no energy/signal can go faster than speed of light" rule is very much maintained. For more information on this, google the difference between "phase velocity" and "group velocity" of light, which will give you some insights.
The problem is that when introductory physics is taught, the difference between these different velocities is not mentioned (phase velocity != group velocity != photon velocity) And of course, news articles never mention it!!
I was going to mod, but I guess a reply is better.
regarding point (3)-- "ess temperature = less energy (e). the speed of light (c) decreases at the same rate as the square root of e." I call shenanigans. c is a constant here to relate the conversion of mass to energy (and vice versa). E does NOT reference heat energy.
If it did, the speed of light would increase for hot objects (and on hot days). Time effects would be experienced by stars and nuclear reactors.
1) Wavelengths are too big: 1 micron is now a large number, and optics doesn't work much smaller than this.
This poster is correct. Since I have a Ph.D. in the field and the parent obviously knows something about optics, I might as well respond to the parent's critics.
IR photons are BIG. Forcing light to bend around corners is difficult. A waveguide must have a very high index of refraction if it is to be used to bend light within a reasonable radius. To the extent a Bose-Einstein Condensate helps this problem is encouraging if you don't mind cooling your computer to 2 millikelvin.
The speed of these optical computers always seems to come down to limitations of the silicon processors that work in conjunction with the light.
It's just a Bose-Einstein Condensate. These projects take time. While we are enamored with this BEC project, some poor grad student is working on carbon doping. Higher doping might improve the world of electronics far more than another optical computer claim.
I visited Hau's website and did, though, enjoy her papers. I just don't think the press release accurately portrays the low engineering potential of this work.
No it doesn't. The speed of light and the speed of light are actually two different things.
One is a constant, the maximum speed at which anything can travel. For example, light travels at that speed in a vacuum.
The other is the actual value of light in specified circumstances, for example the speed of light in air or the speed of light in glass. Light travels slower through material compared to a vacuum, but that doesn't mean that the constant as mentioned above changes. It just means that the speed is bounded by the constant.
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If we can slow light to somehow make our "units" twice as long, we'll never get in a war again. Their women won't consider our lives expendable.
That kind of blows the constant out of the water.
Refer to my other post (in reply to GP). The "speed constant" is very much intact, when you remember that it refers to photon velocity, not the group velocity of a light beam. The group velocity can have any value: 0, positive, negative, less than c, greater than c, etc. (just like, as another poster points out, the "movement" of a shadow can have any value). The fact that the envelope of a photon interference pattern (the group velocity) travels at a certain velocity does not imply that the constituent photons were travelling at this velocity. Thus, signals still cannot be transferred at these apparently superluminal speeds.
We also now know for a fact that instantanious travel is physically possible via quantum entanglement, across any distance. Proven in a lab.
Not exactly. What has been proven in a lab is that there are inescapable correlations in entangled quanum systems. However, due to the very nature of quantum mechanics and entanglement (and things like Heisenberg indeterminacy), there is no way to use these correlations to send signals or energy instantaneously. Yes quantum correlations operate over arbitrary distance, and yes they appear to operate "instantly"... but although the extent of correlation is always predictable (using quantum theory) the exact outcome of a particular experiment is not predictable, making it impossible to use this technique to send "faster-than-light" transmissions.
Physics is amazing and exciting enough without the hyperbole and misinterpretations that often weigh it down.
Using the same apparatus, which contains a cloud of ultra-cold sodium atoms, they have even managed to freeze light altogether. Professor Hau says this could have applications in memory storage for a future generation of optical computers.
I'll assume the store medium will need to be kept at this "ultra-cold" temperature for data to be safely stored. What if the cooling system fails (e.g. power failure, compressor failure, etc.). Or what if you don't have the resources to maintain this ultra-cold environment?
I think I'll stick to cheaper and more reliable store mediums like optical disks or solid state memory.
That isn't just an optical computer, that is where we live. Inside a frozen photon! Think about it. What does relativity tell us about the nature of the universe at the speed of light? It tells us that as we approach the speed of light, space and time compress. At the speed of light, they cease to exist! Google the twins paradox for more information. Essentially, this has been proven to be true with atomic clocks calibrated with each other, one on the ground and one aboard a plane traveling several times the speed of sound. Later when compared, they deviated precisely with what Einstein predicts in his equations, thus confirming Relativity.The twins paradox is a true property of our universe. Obviously light is a most transcendent property of the universe. Whereas everything else appears to slow and contract in relation to it, it alone remains constant. Nothing of mass can travel at C but light can. It has a unique perspective, if you can imagine it. It does not see a universe, indeed it sees nothing at all, thus how does it move? It does not, it rests as a single solitary photon. Like a frozen photon, a BEC, or Bose-Einstein Condensate. These are the exact properties of our universe! Gentlemen, I say to you, we exist within a Bose Einstein Condensate!!! Incidentally, they're saying Moore's law is dead or at least MIA. But all this, according to Ilya Prigogine coincides perfectly with the law of dissipative structures. Moore's Law is simply following a traditional bell curve. But from within it, scaffolding ever higher, comes the seeds of the next bell curve! In this case, it would appear optical computers are it...
The speed of light in a vacuum is constant. When light enters any material, it slows down. The amount it slows down is related to the refractive index of the material. These 'slow light' researchers have managed to create very weird materials that have extraordinarily high refractive index at low temperatures. This causes the light to slow down a lot, or even to stop (for materials where the refractive index becomes infinite).
Kudos to whoever is giving out low mod points to people whose jokes completely blow. I have seen "Funny,5" way too many times for observations that are just too painfully unfunny to read.
>In Soviet Russia, light freezes you!!
God, please stop.
As you say, there are no good low power nonlinearities. High power nonlinearities are easy to find -- the vacuum is nonlinear at high enough power levels. But I know of no optical nonlinearities which are functional at low -- or even modest -- power densities. This is important because it affects the packing density of the circuitry (see below).
The article uses a faulty metric -- the speed of propagation of signals is not the important criterion for designing a computer, but rather the delay in reaching the next gate. This depends as much or more on the density of the components (and the dimensionality of the construction technique) as it does on the speed. If components are spaced a foot apart, then it takes more than a nanosecond to reach them no matter what. While it is true that properly buffered CMOS on-chip wiring is only about 3% of the speed of light, the density (and required low power) of CMOS allows billions of gates to be reached in a nanosecond. Optical technology has a LONG WAY to go in reaching this point, let alone exceeding it. By then, 3-D silicon will make these numbers dramatically higher.
Also, superconducting on-chip interconnect will make on-chip silicon wiring dramatically faster (10x?) and is a much much easier technology that BEC.
But the physics is sure cool.
Wait, if this is just refraction, then the light isn't slowed at all, right?
No, it is. Mentioning refraction is a little odd, as refraction is caused by the slowing of light, not the cause of the slowing of light.
Once you're out of free space, the speed that an electric field can move can be hugely affected by density, etc.
Think of it this way: in a high optical density material, light is so slow because it has to drag electrons around as it moves. Light's an electromagnetic field, after all, and electrons have an electric field.
Now, you could *also* consider on a very, very small scale (sub-sub-atomic) that the photons are in fact still traveling at the speed of light - it's just that they're interacting so often with the electrons present that their net speed is very, very, very low.
You can do it at close to room temps if you have a gas of atoms and you use lasers and evaporative cooling. There have been experiments done wher BECs were made on a chip.
Light is a fluid if it can be frozen and conducts electricity! This is interesting. If Light can be slowed to a crawl in a Earth refigerator, wouldn't that mean in the Deep Freeze we call Outer Space that's it's already going slower EVERYWHERE? This would mean that Light Speed is only 186,000 on Earth... That Light Speed is really slower than electricity. That my brain is working faster than the Speed of Light. And that THEN we run into a whole host of conclusions: http://www.newpath4.com/formulaeperpetual_perpetua ltimeperpetualspaceperpetualpowerperpetualmomentum perpetualmotion_3plus4equals5.gif & http://www.newpath4.com/forsalespacecraftenginecon stantpowertheory.htm .
The definitions are all being sucked into a Black Hole: http://www.newpath4.com/anwar_drillitfastdrillitgo odforgetaboutthneighborhood_anwar.htm .
Heck, with the Speed of Light now in question it means there's a very real possibility I'm completely right and the REST OF YOU ARE ALL COMPLETELY WRONG. hehehehehehehehehe
This has been another post by Woodrow Riley, who never claimed to be another Einstein but may be anyway.