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Rydberg Blockade

by Xyius
Tags: blockade, rydberg
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Sep4-13, 08:40 AM
P: 436
So, I am a graduate student (first year), doing research on trying to develop a quantum radar. A quantum radar relies exclusively on using a handful of photons (even one single photon) to operate.

Through my research, I have come across "Rydberg Blocking." It seems to be the best way to create photons at the current time. I went to a seminar about Rydberg blocking to learn more about it and just the way the speaker was presenting it, it seemed as though it was still very much in the experimental stages.

I wanted to see if anyone here could shed more light on Rydberg blockage as a means to create single photons. I have a couple of questions.

Do you think that my study in quantum radar is premature? In that, there isn't even an established way to create single photons and my research is already looking to use single photons in an engineering manner.

How well does Rydberg blockage actually work? At the present time, can it reliably create single photons? And what frequency are they emitted at?

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Sep4-13, 12:47 PM
Sci Advisor
PF Gold
UltrafastPED's Avatar
P: 1,908
Is your work related to this:

You should seek out a local expert and ask for suggestions on literature to read. Your reading goal should be to prepare a presentation/report on the state of the art ... this is always a good way to start a new project.
Sep5-13, 07:01 AM
P: 229
A couple of points:

1) The Rydberg blockade effect is fairly easy to explain. The main point is that you take several atoms, spatially close to eachother, such as in a cold gas or ion trap, and then try to excite them using a Rydberg transition. Because the Rydberg states are so large, the dipole moments changes arising from an excitation causes electric fields (via the dipole) large enough to shift all nearlying atoms out of resonance. Thus, only one single atom/ion can get excited because after the first, the others are no longer resonant, and this guarantees a single excitation which is then turned into a signle photon. You can do this whole proceedure without Rydberg states as well, but then you need the atoms to sit much closer together than in a typical gas or ion trap. Certain solid state materials, such as rare-earth doped solids can be suitable for this.

2) If you only want to create single photons as a tool however, you are probaly much better off not using Rydberg blockade, as this, as you note, is still a developing technique. An easier and much more used method is by means of spontaneous parametric down conversion (SPDC), where sources are even commercially available depending on requirements on wavelength/bandwidth purity etc. For a recent overview of single photon sources, see e.g. Eisaman 2011.

Hope that helps.

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