# How many state changes per second could optical computing do

• IsItSo
In summary, the theoretical maximum amount of state changes that one transistor could achieve within one second using optical computing is currently unknown. While there have been suggestions of speeds above 500 GHz, practical applications have been limited to speeds of 10-20 GHz. The use of photons in optical computing presents potential for much higher speeds, but the technology is still in its early stages and further research is needed to determine its full capabilities.
IsItSo
Using Optical Computing, what is the max amount of state changes that 1 transistor could theoretically have within 1 second? I once read that an electrical transistor could achieve 100 billion state changes per second, but I'm wondering what the number is for light, *and what it could theoretically be without each state change requiring any stalling before it can do the next.

berkeman
Anyone?

Google searches suggest ~10-20 GHz for practical applications, but with theoretical speeds above 500 GHz (example).

20 GHz ?... As I mentioned in my opening post, I've read about a 100 GHz electrical transistor, optical transistors (as some sources suggest) should at least be about twice as fast i.e. 200 GHz. (200 billion state changes per second)

One incredibly major problem...
400 million hydrogen atoms fit in an inch
63360 inches in a mile
25 thousand miles around Earth
times 7
= 4,435,200,000,000,000,000 atoms that light passes each second !
Light at least at least at least can therefore give us 4 quadrillion state changes per second (assuming each photon is right behind the other ready to do the next state).
And just think about how much space is in an atom, that's like 2,000 times the number I just gave us above !

IsItSo said:
One incredibly major problem...
400 million hydrogen atoms fit in an inch
63360 inches in a mile
25 thousand miles around Earth
times 7
= 4,435,200,000,000,000,000 atoms that light passes each second !
Light at least at least at least can therefore give us 4 quadrillion state changes per second (assuming each photon is right behind the other ready to do the next state).
And just think about how much space is in an atom, that's like 2,000 times the number I just gave us above !

I don't see the relevance of that to your original Q ?

photons are not like little bullets firing out of a gun

I am not sure the question can be answered.

The switching speed of a transistor will -obviously- depend on the type of transistor. There is no way you could predict the speed of a transistor capable of switching signals at optical frequencies by extrapolating the speed of normal electrical transistors; the technologies will be entirely different.

If the operational principle of the transistor was based on first converting the optical signal to an electrical current and then back again it would be much slower than an all-electrical transistor.

Also, there are electrical circuits (simple flip-flops based on superconducting electronics) that can operate at hundreds of GHz

mfb said:
Google searches suggest ~10-20 GHz for practical applications, but with theoretical speeds above 500 GHz (example).
Can't get the link to work. Do I need a subscription ?

IsItSo said:
(assuming each photon is right behind the other ready to do the next state).
Photons do not even have a well-defined position. Your calculation has no relevance to optical computing.
BvU said:
Can't get the link to work. Do I need a subscription ?
No subscription, but the link doesn't seem to work. I went there via google -> some captcha -> that PDF, apparently the direct link doesn't work, I'm not sure if the captcha link help. If not, search for "Photonic temporal integrator for all-optical computing sitesapublishing.org".

There are very fast transistors, but you need more than a very fast transistor to make a useful circuit.

BvU
So, the transistor described here
http://science.sciencemag.org/content/early/2013/07/03/science.1238169.full
seems to be based on atomic states of cesium-133, | g 〉 = | 6S1/2,F = 3,mF = 3 〉, | d 〉 = | 6P3/2,4,4 〉, | s 〉 = | 6S1/2,4,4 〉, | e 〉 = | 6P3/2,5,5 〉
The paper doesn't really say, but I suppose the switching frequency must be slow compared to all of the transition frequencies involved here.

NIST atomic spectra database gives the 6S1/2 - 6P3/2 transition as 852.11 nm, which would be a frequency of 3.5182*10^14 Hz. On the other hand, the hyperfine transition of cs-133 is 9.192631770*10^9 Hz, which is much, much slower. I suspect you will have problems bleeding of the gate photons and the main path if you operate near this frequency.

Because if they travel that far each second past that many atoms, while possibly doing as you said some "teleporting" i.e. doesn't take 4 Quadrillion moves, then if we send lots of photons to our target some will teleport at spots where the other didn't so you end up with 4 or more quadrillion.

Nevertheless, in our current optical computing I don't see why we haven't yet got such happening i.e. 4 quadrillion states per second. Maybe they didn't plan for it? They should be able to go a lot higher.

Photons don't teleport. You can transfer the quantum state of one photon to another photon, which is called teleporting, but that needs a classical information transfer and the whole process is slower than the speed of light.

Photons do not have a position - do you understand that part? Your whole speculation is based on an incorrect assumption.

So you're saying I should ignore the amount of atoms a photon passes in 1 second, and focus on what the latest foreseeable optical computing speed of states per second it is able to achieve? But then we truly won't theoretically know a definite number like I explained above...

So 200 billion state changes will probably be possible, but possibly not any higher in the future? (consider this number [200 billion], and look at how many atoms a photon passes each second - 4 quadrillion (+atomic-space), that's a STRANGE difference)

IsItSo said:
So you're saying I should ignore the amount of atoms a photon passes in 1 second, and focus on what the latest foreseeable optical computing speed of states per second it is able to achieve? But then we truly won't theoretically know a definite number like I explained above...

So 200 billion state changes will probably be possible, but possibly not any higher in the future? (consider this number [200 billion], and look at how many atoms a photon passes each second - 4 quadrillion (+atomic-space), that's a STRANGE difference)

you are throwing out these crazy numbers and making wild assumptions without any backing references
you need to stop that please

IsItSo said:
So you're saying I should ignore the amount of atoms a photon passes in 1 second
No, I say that number doesn't exist. It's like asking how many atoms an invisible unicorn is made of.

How it is like asking how many atoms --- an invisible unicorn is made of, when I said the "invisible" photon is passing the (yes also fuzzy) 4 quadrillion (calculation above) atoms each second?

IsItSo said:
How it is like asking how many atoms --- an invisible unicorn is made of, when I said the "invisible" photon is passing the (yes also fuzzy) 4 quadrillion (calculation above) atoms each second?
Back in post #11 of this thread we said "Photons don't have a position". How does it make any sense to talk about something that has no position passing anything else?

Because we can put a antenna at one place and another at the finish, and it has been calculated that photons reach (only) that far in 1 second, while if you're not in the way of the laser beam you're safe. This means it went a distance and a skinny-width way. The mere fact that it gives you more than 1 state change per second means something.

IsItSo said:
Because we can put a antenna at one place and another at the finish
An antenna does not emit single photons. A laser beam is not made out of individual photons either - it is a coherent superposition of photons, which is a completely different thing. You cannot even count the photons in a laser beam.

Yes ok antennas emit many in all ways, and continuously. Lasers shoot many out. My last reply still stands...

IsItSo said:
Yes ok antennas emit many in all ways, and continuously.
Not necessarily.
IsItSo said:
Lasers shoot many out.
No they do not.

If you want to learn: great!
If you want to ignore what everyone is trying to tell you, and rephrase your questions based on wrong assumptions over and over again: I don't think that is helpful. As long as you don't stop that approach, you won't make progress.

Let me deeply go through this. The element emits photons from all sides. Keeps doing so. And can focus them.

Doesn't my point stand that they will get to a certain distance in 1 second, and only come out of the long laser hole, and gives us more than 1 state change per second?

I realize we only can currently implement so many state changes (200 Billion optically?), But with the above (and the amount of atoms they pass) I can't see how it doesn't hold ground that they could give us 4 quadrillion state changes.

What if the optical transistors were atoms, so that when the photon leaves (and travels on that far distance) the next can come on in and quickly change the state?

IsItSo said:
The element emits photons from all sides. Keeps doing so. And can focus them.

no, they emit electromagnetic radiation ... as I said and others have also tried to tell you
Photons are NOT like little bullets shooting out of a gun

IsItSo said:
Doesn't my point stand that they will get to a certain distance in 1 second, and only come out of the long laser hole, and gives us more than 1 state change per second?

No, see my and others' previous comments

IsItSo said:
I realize we only can currently implement so many state changes (200 Billion optically?), But with the above (and the amount of atoms they pass) I can't see how it doesn't hold ground that they could give us 4 quadrillion state changes.

What if the optical transistors were atoms, so that when the photon leaves (and travels on that far distance) the next can come on in and quickly change the state?
you are still coming from false assumptions

If you want to learn: great!
If you want to ignore what everyone is trying to tell you, and rephrase your questions based on wrong assumptions over and over again: I don't think that is helpful. As long as you don't stop that approach, you won't make progress.

you really have to stop with the bad ideas, information and assumptions, else you are never going to progress in your understanding of physicsDave

mfb
So what's the number for now then, 200-500 Billion per second for optical computing?

500 GHz (500 billion/s) seem possible according to the article I found, but tens of GHz look more realistic for actual computers. Computing happens at the speed of the slowest part (with some exceptions).

If you really push it and have super-incredible nanotechnology and can build with atoms could it reach 1,000 with instant-transistors/etc?

Also, is there any way we can figure this out without testing it?

That's the point of research: figure out what is possible and what is not. While theoretical models (those have to be developed as well) can often give a good prediction, we don't know before we test it.

Try re-reading post #20 and ask yourself if you have taken it on board.
It seems to me that you haven't.

New invention:
If we accelerate up an atom so it travels about 1 mile per second, and film it, we could see it slowly move by each atom! How many atoms does it pass in each mile? Each inch is 400 million hydrogen atoms. That ends up as way more than 500 billion.

IsItSo said:

New invention:
If we accelerate up an atom so it travels about 1 mile per second, and film it, we could see it slowly move by each atom! How many atoms does it pass in each mile? Each inch is 400 million hydrogen atoms. That ends up as way more than 500 billion.
But atoms are not photons. Where is this going - apart from an attempt to justify your original ideas round by the back door. Better to start at the beginning, I think. This stuff has all been thought out by much cleverer people than you and I.

We can do that, but this has nothing to do with optical computing.

IsItSo said:
New invention:
If we accelerate up an atom so it travels about 1 mile per second, and film it,
How is that a new invention? We've been accelerating large numbers of atoms to much greater speeds and filming them, for many decades.

Last edited:
davenn

## What is optical computing?

Optical computing is a form of computing that uses light instead of electricity to perform operations. It utilizes the properties of light, such as speed and parallel processing, to perform calculations.

## How does optical computing differ from traditional computing?

Traditional computing uses electrical signals to represent and process data, while optical computing uses light signals. This allows for faster processing speeds and the ability to perform multiple operations simultaneously.

## How many state changes per second can optical computing do?

The exact number of state changes per second that optical computing can perform is dependent on various factors such as the technology used and the complexity of the operations. However, it is estimated that optical computing can perform state changes at a rate of trillions per second.

## What are the potential applications of optical computing?

Optical computing has the potential to revolutionize various industries, such as data centers, telecommunications, and artificial intelligence. It can also be used for high-speed data processing and encryption.

## What are the challenges facing optical computing?

One of the main challenges facing optical computing is the development of reliable and cost-effective components, such as optical transistors and switches. Another challenge is integrating optical computing with existing technology and infrastructure. Additionally, there are still limitations in terms of scalability and programming for optical computing systems.

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