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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."
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).
Iran captures three CIA agents
Try running a standard LED in liquid nitrogen once. It gets seriously brighter.
But it won't have the same effect on your friends.
"But all your emitter and collector are belong to me!"
I thought the speed of light was absolute? What am I missing here?
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)
What you reap is what you sow
While this may not work (and I emphasize may, isn't it just a wee bit early to pronounce it impossible, implausible, or impractical?
Ben Hocking
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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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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.