## Tuesday, May 03, 2005

### Optical signal processing

I decided to see a real physics talk - a colloquium about optics and experiments.

Kelvin Wagner from University of Colorado at Boulder was speaking about optical signal processing. While Eli Yablonovitch complained about the end of the semiconductor roadmap and the disaster that it will bring to the society, Kelvin Wagner was celebrating it.

In fact, the digital processing and electronics is a competitor of optical signal processing. The people in electronics are getting much more money, and it is only because they are cheating, Wagner was explaining: for example, they always use a fuzzy picture of the Los Angeles area obtained by optical signal processing if they want to show that their digital methods are superior.

What is optical signal processing all about? Wagner chose some old-fashioned optical computers as his first example. They were able to factorize the Mersenne number 2^{79}-1 decades ago, by a sophisticated combination of gears, holes, and light rays - this was about 1 million times faster than any other method available at that time. Well, today we have to look (digitally) for larger Mersenne numbers in order to find greater primes.

Wagner also showed the Fourier transform of various letters and argued that the methods of optical signal processing are useful for pattern recognition - and for some tasks, they are superior over the digital techniques.

This field of physics uses various two-level atomic systems. If the splitting is fine (e.g. hyperfine structure), the system is suited for long-term memory purposes. For example, Wagner argued that a system may be used to store 10^{14} bits in a piece of crystal (the memory decays after one day or so). On the other hand, other atomic systems with bigger energy splittings are appropriate for computing, fast response, and the application to wideband optical processing is the natural one. One is expected to use these methods in the religion, for example, to localize the signals from the ET aliens ("SETI").

One of the key methods he discussed was the so-called spectral holography. This concept is analogous to the usual, spatial holography (which itself is analogous to holography in quantum gravity). Instead of the interference pattern as a function of the position on the screen, which occurs in spatial holography, spectral holography creates "interference patterns" in the space of frequencies - in other words, it is about modulation. Such modulation may be obtained by superposing two signals that are shifted in time.

They are working to increase the bandwidth, the resolution - in order to solve massively parallel processing tasks - and he expects that unless electronics will cost 100% of the GDP, the optical signal processing over may take over around 2020, at least in some applications. I have not understood most technical details of the talk well enough to illuminate them.

1. Lubos said: "I decided to see a REAL physics talk - a colloquium about optics and experiments."

Good you realize that the super string stuff you have been working for are not REAL physics.

Wagner's claim that the elecronic people steal their optically processed images are just jealous with no substance to the claim.

Principlely optical processing is certainly faster. The fastest is certainly quantum computing. The whole universe is a giant quantum computer and everything is decided quantum computingly. But flexibility makes the electronic way of digital processing the only practical solution so far.

Quantoken

2. Quantoken, there you are! Come to my office first thing tomorrow morning, you naughty lunatic. You have to pick up your medication...

3. Dear "Your psychiatrist": tempting though it may be to laugh at Quantoken, and I must admit that I had a good laugh at your post, one should also [between giggles] ask whether it is proper to poke fun at people who are mentally ill. Perhaps it would be more humane just to ignore him?
HAHAHAHAHAHAHAHA!!!!!
Sorry, sorry.......

4. One of the key methods he discussed was the so-called spectral holography. This concept is analogous to the usual, spatial holography (which itself is analogous to holography in quantum gravity). Instead of the interference pattern as a function of the position on the screen, which occurs in spatial holography, spectral holography creates "interference patterns" in the space of frequencies - in other words, it is about modulation. Such modulation may be obtained by superposing two signals that are shifted in time.

I wonder what Gerard 't Hooft thinks of this?:)

I even noted the hint of sarcasm, so
I wonder what you were thinking
Lubos when you said this.

If Quanto had read it a little deeper he might have realized what he was missing? The quote is specific.

So anyway, in thinking signal processing would seem a interesting topic if held in context of some new method (photosythesis as a process, at such high energies?).

How would transmitted signals have been mixed. These are entanglement issues? The collider view, as the string, incorporates a lot of other signals, yet it is all harmonious. You see Quanto?:)

To initiate such signal processing from the idea of particle inception, from blackholes, how would you measure this? I think you point to the issue that needs to be resolved.

Smolin and others understand this as well, and this is the progresssive step taken. Yet they have not gone as far as the quantum issue in terms of quantum gravity? Why Glast is important from their, and the calorimetric view. Everyone feels happy and in Cern and they understand this well?

Strings holds a valuable theoretical position, in regards to quantum gravity. Also, raises, new difficulties in terms of how far we can actually go? Why is it Gerard 't Hooft feels unsure?

This is where I sense Peter Woit and others feel safe holding onto the rail of computerization problems. You too.:)

This topic certainly raises important questions. Continue to push forward Lubos.