
Light-based computers in development - parwell
http://www.kutv.com/news/features/top-stories/stories/Light-based-computers-in-development-to-be-millions-of-times-faster-than-electronics-based-designs-133067.shtml#.VV0PMa77tC1
======
zamalek
> The key advantage of light, made of photo[n]s, is it’s the fastest thing you
> can use to transfer information according to the professor.

I wish people would stop spreading this exaggeration. ~~Electrons~~ Electronic
signals move at 0.66c. In practice 1c is unlikely to provide the most
significant gains.

The key benefit is actually the energy efficiency that the article barely
mentions, as well as massive reduction of interference within circuits (which
is why you have to up the CPU voltage when you overclock).

~~~
weland
I have to nitpick because that's a very frequent misconception as well:
electrons, in fact, move very slowly in metals and semiconductors (a few cm/s
at best). It's the electromagnetic waves that move so fast (depending on the
material, it's going to be anywhere between 0.5c and 0.9c in most everyday
appliances), but the electrons themselves are really slow.

~~~
zamalek
Thanks, edited to clarify.

~~~
weland
You're welcome :).

------
TTPrograms
The main problem is still getting strong optical nonlinearity to build optical
only transistors. Right now best case 1 in 100 photons will be affected by
most "switches". There's been some research using various resonators to
enhance the nonlinearities, but that's really the big problem to solve right
now.

There's also scaling issues - we have 20nm electrical switches, which is
almost 50 times smaller than the wavelength of visible light, so you either
need to go to deep UV or confine light to area much smaller than the free-
space wavelength, which presents its own challenges.

My personal interest in optical computing is mainly in building optical
quantum computers, in which case the cost/size/power of solving these
challenges could be well worth it due to the scaling advantages of multi-qubit
entanglement. Classical optical computing does not really seem that worth it
if we need to build computer chips that are 1000 times bigger and run each
operation on average 10^8 times to get a valid result, although the clock
speed and power benefits would be nice.

~~~
hvidgaard
If efficiency is vastly improved, we can stack the layers and increase
frequency by quite a bit. Even if the processor becomes a 10cm x 10cm x 10cm
cube, it's okay as a proof of concept.

It's an interesting approach to overcome the inherient limitations of electron
based circuits.

~~~
TTPrograms
Again, right now 1 in 100 photons will interact with an optical switch. This
effect multiplies with each level of transistors. This means you have to "run"
your circuit potentially something like 10^100 times to get all of the
transistors in your path to work on the same photon.

That's pretty rough.

------
Aardwolf
> Light-based computers in development, to be millions of times faster

When will we see this millions time faster computers commercially available?

Maybe around the time when the thousands-times faster internet and 100 times
larger batteries from articles I read years ago are available...

~~~
jeffbr13
Are you being optimistic or pessimistic? It's only been 15-20 years since 56kb
dialup was the norm, and Tesla are doing pretty well at the moment.

~~~
Aardwolf
Not pessimistic about technology, but about exaggerated article titles :)

