Photonic computers

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rhoenix
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Photonic computers

Post by rhoenix »

University of Bath wrote:Research project could help create computers that run on light

An £820,000 research project begins soon which could be an important step in bringing the dream of photonic computers – devices run using light rather than electronics – onto the desktop.

Physicists at the University of Bath will be looking at developing attosecond technology – the ability to send out light in a continuous series of pulses that last only an attosecond, one billion-billionth of a second.

The research could not only develop the important technology of photonics, but could give physicists that chance to look at the world of atomic structure very closely for the first time.

In June Dr Fetah Benabid, of the Department of Physics at Bath, will lead a team of researchers to develop a new technique which would enable them to synthesise ‘waveforms’ using light photons with the same accuracy as electrons are used in electronics. Waveform synthesis is the ability to control very precisely the way that electric fields vary their energy.

Ordinarily, electric fields rise and fall in energy in a regular pattern similar to the troughs and crests of waves on the ocean, but modern electronics allows a close control over the shape of the ‘wave’ – in effect creating waves that are square or triangular or other shapes rather than curved.

It is this control of the variation of the electric field that allows electronic devices such as computers to function in the precise way needed.

But electronics has its limitations, and the development of ever smaller silicon chips which has allowed computers to double in memory size every 18 months or so will come to an end in the next few years because the laws of physics do not permit chips smaller than a certain size.

Instead, engineers are looking to the science of photonics, which uses light to convey information, as a much more powerful alternative. But so far photonics can use light whose waveform is in one shape only – a curve known as a sine wave – and this has limited value for the communications needed to run a computer, for example.

The Bath researchers want to allow photonics to create waveforms in a variety of different patterns. To do this, they are using the new photonic crystal fibres which are a great step forward in photonics because, unlike conventional optical fibres, they can channel light without losing much of its energy.

In the research, light of one wavelength will be passed down a photonic crystal fibre which then branches off in a tree-like arrangement of fibres, each with a slightly separate wavelength, creating a broad ‘comb-like’ spectrum of light from ultra-violet to the middle of the infra-red range.

This broad spectrum would allow close control over the electric field, which is the basis of conveying enormous amounts of information that modern devices like computers need. They are funded by a grant from the Engineering and Physical Sciences Research Council.

“Harnessing optical waves would represent a huge step, perhaps the definitive one, in establishing the photonics era,” said Dr Benabid.

“Since the development of the laser, a major goal in science and technology has been to emulate the breakthroughs of electronics by using optical waves. We feel this project could be a big step in this.

“If successful, the research will be the basis for a revolution in computer power as dramatic as that over the past 50 years."

Dr Benabid said that the technology that could be built if his research was successful could, for instance, make lasers that operate at wavelengths that current technology cannot now create, which would be important for surgery.

The continual series of short bursts of light will not only dramatically affect technology - it will also advance physics by giving researchers the chance to look inside the atom.

Although atoms can now be “seen” using devices such as electron microscopes, it has not been possible to examine their fast dynamics.

By sending the light in short bursts into an atom, they will be able to work out the movements of electrons, the tiny negatively charged particles that orbit the atom’s nucleus.

This may throw light, literally, upon the strange quantum world of sub-atomic particles, which have no definite position, but are only ‘probably’ in one place until observed.
This certainly sounds fun, and interesting to follow.

Also, these types of computers would worry a bit less about EMP's. Heh.
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Post by Dennis Toy »

The prospect of photonic computers is really exciting. I wonder if you could also use this to create holograms like in Star Trek.
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Post by Stark »

Photonic computers /= open-air holograms.

It's an interesting direction of study. Seems a lot more 'general purpose' than quantum computing. The article doesn't go into much detail about how successful they are right now, though.
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Post by KrauserKrauser »

See, this is the sort of shit I would like to spend my money on if I won the lottery. There is even the outside chance of something marketable resulting from the research.
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Post by Soontir C'boath »

Stark wrote:It's an interesting direction of study. Seems a lot more 'general purpose' than quantum computing. The article doesn't go into much detail about how successful they are right now, though.
Well how can they be if they haven't begun yet? :P

How/why does the shape of the wave affect the ability of electronics to perform?
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Post by drachefly »

You want the wave to stay the same as it moves through the path. If you use a pure sinusoid, that would stay the same... but if it's a pure sinusoid, you never get to convey any information with it. So that's out.
So you need to tailor pulses that can be sent, one after another, that don't blur out and run into each other.
As it turns out, some shapes of wave do this. Others do not. Which shapes do this depends on the specifics of the material you're sending it through.

Those which maintain form are called 'solitons'.
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Post by Molyneux »

Interesting...I don't think I have even close to the requisite amount of knowledge to understand this, but it certainly sounds cool.

Wouldn't we have to be VERY careful to seal these things airtight, though? A speck of dust could screw up the whole CPU...
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Post by Duckie »

Molyneux wrote: Wouldn't we have to be VERY careful to seal these things airtight, though? A speck of dust could screw up the whole CPU...
Most high tech machinery is fragile as such. There's a tradeoff in reliability for effect- you could dropkick a mechanical calculator and it might work but you best not mess up the quantum calculator by breathing on it.

Plus, vacuum pumps are decades old. Just seal it up tight and don't break the case. No air, no dust.
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Post by Wyrm »

Molyneux wrote:Wouldn't we have to be VERY careful to seal these things airtight, though? A speck of dust could screw up the whole CPU...
The same is true of a hard drive; one speck of dust and the heads crash, and your data go bai-bai. Yet those things are ubiquitous in modern computing, less than a cent per MB, and can last for years, and that's mostly because it's still a mechanical device. It's just one more airtight chamber in a computer.
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Post by Spyder »

I'd like to see how much heat an optical chip would give off. I'm suspecting not much.
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Post by Wyrm »

Spyder wrote:I'd like to see how much heat an optical chip would give off. I'm suspecting not much.
If they build it like a regular computer, every 2-input photonic logic gate will need to sink the energy of at least one photon train. Over millions of gates, this can add up quickly.

The absolute lower limit of computation is kT ln 2 per bit erased. Most logical gates erase at least 1 bit of information (except the inverter).
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Post by drachefly »

In regular computers, each gate is a voltage source that sinks into the input leads of the next switch. From what I've seen of photonic gates, the switching is a lot more hands-off. Also, they could use a mirror to deflect the beam onto a distant object which acts as a heat sink. That would handle the thermodynamics without overheating the computer.
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Post by Tolya »

I wonder when will the marketing monkeys start advertising their computers as 'faster than light'...

Im signing up for such a rig. I could finally play Supreme Commander without hickups on 200x200km maps, which would be damn fucking cool. And raise the unit cap to 5000...
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Post by Wyrm »

drachefly wrote:In regular computers, each gate is a voltage source that sinks into the input leads of the next switch. From what I've seen of photonic gates, the switching is a lot more hands-off. Also, they could use a mirror to deflect the beam onto a distant object which acts as a heat sink. That would handle the thermodynamics without overheating the computer.
Only if the swtiching process of the gate itself is truly reversible can this be done. If the photonic gate itself alters the second beam such that the process is irreversible, then it is the gate itself that is responsible for destroying the information, and the gate itself takes the kT ln 2 heat hit, possibly more depending on the switching process.

Not that kT ln 2 of heat per bit is a particularly big hit at normal computational temperatures, mind you. Current electronic computing is nowhere near this efficient.
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