To hold the photon's shadow
Hi, guys. I thought I would talk a bit today about my current direction of research. It's a pretty simple goal to state: we want to hold the photon's shadow.
Of course, photons don't have shadows: if you send two laser beams together they will pass right through each other, each progressing as though the other weren't there.
That's true to a point. When the laser beams start getting strong they temporarily (or sometimes permanently) change the nature of the matter they traverse. When they are (or if they were) really strong one must begin to say that they change the nature of space itself.
Those changes to media through which beams propagate can then allow one beam to have an indirect impact on a second beam. There is now a shadow.
This type of change can be used for optical switches. People can make LCD screens (which are just large arrays of liquid crystal optical switches) that are activated and deactivated by light.
But it can also happen in air. If the laser is strong enough it will change the properties of the air it traverses--density, temperature, and so on--and that will change the index of refraction of the air. Just like heat wafting up from the fire leaves a shiny, plasticy shadow, so can heat from the heart of a laser leave a more structured, plasticy shadow.
A moderately strong (100 mW--somewhat dangerous) laser produces around 3*10^17 photons per second (here I'm assuming visible light). Let's see: 9 zeros means billion, 12->trillion, 15-> quadrillion. So the laser produces around 300 quadrillion photons per second. Your eyes are so sensitive they can see a single photon if properly adjusted to the dark. That's why shooting them with lasers is a bad idea.
Anyway, the effects I've been talking about would be hard to observe from a moderately strong laser. Crank it up by a factor of 1000 or 1000000 and keep the profile reasonably tight and you should see them alright.
If we want to use the photon's shadow to build quantum circuits and make precision measurements we need to go the other direction. Instead of looking at the net shadow of 300 quadrillion photons we want to see the shadow of a single photon. Obviously, that isn't going to happen in air.
Or at least not in ordinary air. It just may happen with a specially prepared gas. Imagine a set of identical atoms. Now smack them with highly ordered light rays of specific wavelengths and specific strengths coming from specific directions. The light interacts with the atoms and the atoms with the light and the whole, beautiful as it is, is different than the sum of the parts. What you have now is an artificial construct, an ephemeral chimera. What are its properties? They depend on the nature of those light rays. In other words, you have some ability to control its properties.
We know what properties we want: we want the nonlinear index of refraction to be such that shadow of the photon would be enhanced over the shadow it would have in ordinary air by about a factor of one quintillion. And we want the chance that the photon will be absorbed to go to zero. Now it is a question of getting as close as possible to what we want.
All in all, it's a pretty cool project . . .
Of course, photons don't have shadows: if you send two laser beams together they will pass right through each other, each progressing as though the other weren't there.
That's true to a point. When the laser beams start getting strong they temporarily (or sometimes permanently) change the nature of the matter they traverse. When they are (or if they were) really strong one must begin to say that they change the nature of space itself.
Those changes to media through which beams propagate can then allow one beam to have an indirect impact on a second beam. There is now a shadow.
This type of change can be used for optical switches. People can make LCD screens (which are just large arrays of liquid crystal optical switches) that are activated and deactivated by light.
But it can also happen in air. If the laser is strong enough it will change the properties of the air it traverses--density, temperature, and so on--and that will change the index of refraction of the air. Just like heat wafting up from the fire leaves a shiny, plasticy shadow, so can heat from the heart of a laser leave a more structured, plasticy shadow.
A moderately strong (100 mW--somewhat dangerous) laser produces around 3*10^17 photons per second (here I'm assuming visible light). Let's see: 9 zeros means billion, 12->trillion, 15-> quadrillion. So the laser produces around 300 quadrillion photons per second. Your eyes are so sensitive they can see a single photon if properly adjusted to the dark. That's why shooting them with lasers is a bad idea.
Anyway, the effects I've been talking about would be hard to observe from a moderately strong laser. Crank it up by a factor of 1000 or 1000000 and keep the profile reasonably tight and you should see them alright.
If we want to use the photon's shadow to build quantum circuits and make precision measurements we need to go the other direction. Instead of looking at the net shadow of 300 quadrillion photons we want to see the shadow of a single photon. Obviously, that isn't going to happen in air.
Or at least not in ordinary air. It just may happen with a specially prepared gas. Imagine a set of identical atoms. Now smack them with highly ordered light rays of specific wavelengths and specific strengths coming from specific directions. The light interacts with the atoms and the atoms with the light and the whole, beautiful as it is, is different than the sum of the parts. What you have now is an artificial construct, an ephemeral chimera. What are its properties? They depend on the nature of those light rays. In other words, you have some ability to control its properties.
We know what properties we want: we want the nonlinear index of refraction to be such that shadow of the photon would be enhanced over the shadow it would have in ordinary air by about a factor of one quintillion. And we want the chance that the photon will be absorbed to go to zero. Now it is a question of getting as close as possible to what we want.
All in all, it's a pretty cool project . . .
posted by Douglas H. at 7:59 AM
6 Comments:
I may have to read through that a few more times, or just wait till you can answer some questions . . .
Ask away! Probably if you have questions other people will too and answering them will help me feel like a communicated a bit better.
Doug, that is the kind of thing I love to hear you waxing poetic and excited about, the physicist in you. Make me get excited.
What. You're not excited yet?
What if I told you that we might get to use cool things like atom beams and big lasers?
In all honesty your comment underscores the fact that I have a serious branding problem. My brand is physics but that is where only a small part of my heart is. I'm working hard to figure out who I am and what I want to do with this short life and the work isn't done. In the meantime I can finish up this thing. Hopefully I can anyway.
Always before I have been happiest when I have found plenty of challenge. For the past two years my biggest challenge has been patience. I know my projects are cool. And there are challenges involved. I know that relativity is just plain awesome. Maybe just learning and doing cool things isn't enough anymore. Was it ever?
Doug, our previous Chief Medical Informatics Officer had a PhD in physics. You could easily enter the field with your current PhD (and MS from JH). I personally recommend putting all your energy into your physics PhD first. Finish as strong as you can (in your case an a A++ instead of just an A+).
Rick, that's good sound advice. I think I'll take it.
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