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You know how cool this is?! It should be possible to set up an experiment with entangled photons and use your eyes as the detector. We could literally see quan

by IIAOPSW 10y ago

You know how cool this is?! It should be possible to set up an experiment with entangled photons and use your eyes as the detector. We could literally see quantum mechanical behavior with our own eyes! Pardon my crudeness but how fucking cool is that!

markcerqueira 10y ago
Just tried this experiment at home! Felt about one photon in my left eye and two in my right in one minute!! :D
- nsxwolf 10y ago
  What's your source of single photons?
  - markcerqueira 10y ago
    Forgot the margin of error! +/- 2 photons!!! :D :D :D
  - VLM 10y ago
    A quarter century ago we used a well characterized laser at a known power level that given a very precise wavelength and total power results in a very precise number of photons per second, like on the order of somethingE15 photons per second. From what I remember of filters neutral density transmission is log, so its pretty easy with a laser power meter to prove a ND2.0 outputs 1e-2 of input photons and turns the remainder of photons into heat or reflects them. Show an easily measurable somethingE15/sec photons out of a laser and the meter will read 1% power. Now you can buy neutral density filters of all kinds of measurable density. And filters stack, 1% of 1% is what you'd expect, not something crazy like average or RMS or whatever. So my numbers above might be all messed up but conceptually it boiled down to create a "normal scale human brightness" fountain of a knowable number of photons per second and filter it such that theoretically about one sneaks thru every second or once in awhile or whatever. Unfortunately we didn't have time to fool around with looking at it. From memory, I think we used it as some kind of quantum proof lab. So part one is diffraction patterns prove photons totally are definitely waves, and part two of the lab was this really sensitive photometer (essentially a geiger counter for photons) shows that each light photon is a distinct and countable bullet. And look, varying the density of the filter stack has no effect on the energy of each photon bullet it merely affects the rate at which they arrive isn't quantum mechanics spooky and wonderful? If that wasn't what we did with it, it probably should have been, or at least from memory I think that's pretty close to what we did. I suppose in the modern era lasers are a lot more powerful so you would need a better filter and rather than the weird vacuum tube photon sensor you'd just use a COTS solar panel and measure the single electrons produced by the single photons (within solar panel efficiency correction factor etc) You know whats really fun to do with quantum mechanics, is do a dual slit diffraction graph with a source that's like 1 photon per second so you know the apparatus only has one photon in flight at any given time. Rather than doing the two parts of my undergrad lab separately, do them together. In my infinite spare time that would be fun to build at home. I would imagine it would take a long time to gather the data, perfect for home amateur scientist types. I know what that graph looks like, and it freaks people out every time.
    - nsxwolf 10y ago
      I only understood a tiny bit of what you said, but I do get freaked out by the double slit experiment with single photons. It's like the photon is interfering with versions of itself in alternate universes.
Immortalin 10y ago
Can this be used for neutrino detection? Instead of ice + light sensor, you use sweatshop + human. Someone should do the math, perhaps in the right country it is cheaper to use mass indentured labor than electronics. (This is just a thought experiment, I am not supporting sweatshops)
- flukus 10y ago
  I think the mental pressures from confining people into completely dark rooms underground for hours on end might produce some false positives. Probably wouldn't tell us much about the characteristics of the light either.
  - dalke 10y ago
    We've done it before. Geiger and Marsden were the first to observe what is now often called the Rutherford gold foil experiment, https://en.wikipedia.org/wiki/Geiger%E2%80%93Marsden_experiment https://en.wikipedia.org/wiki/Geiger%E2%80%93Marsden_experim... . They used a microscope to look at the flashes of fluorescent light created after the alpha particle scatters from the foil. (We could repeat this experiment in upper-level physics lab class. The teacher said it takes about 20 minutes for the eye to become sensitive enough to see flashes. He said then that the eye could see a single photon. Looking around now, I confirmed that papers of the time only said that was needed no more than 10 quanta.) So while there may be some false positives, it's not high enough to make it useless.
- antognini 10y ago
  I seem to remember doing a similar problem in an order of magnitude astrophysics class I took. We calculated that there were good odds that at least one person on the planet detected a neutrino from Tycho's supernova when it interacted with the vitreous body of the eyeball. (This is from memory, so don't quote me on it --- I may have remembered the sign wrong!)
- Cerium 10y ago
  This concept is explored in Neal Stephenson's Anathem. To avoid spoilers, I will be vague. One of the orders in the novel runs such an experiment. They have many people watching a pool or water or ice, and they independently record flashes they may see. If everyone sees the same thing, then they have captured a neutrino.
StanislavPetrov 10y ago
>We could literally see quantum mechanical behavior with our own eyes! That occurred to me as well as I read that article. It certainly raises some interesting questions about potential observations and wavefunction collapse.
noobermin 10y ago
Just to note, they do hint at that in the end of the article, so you bet your socks scientists are thinking about it. It certainly was one of the first thing that entered my mind.
grondilu 10y ago
If you see anything it would mean that the photon had been entangled with your retina, your visual nerve and your brain. All those being macroscopic objects, you could not see any quantum behavior. I'm not sure what would you expect to see anyway. A photon in two places at once? That's not how it works. The wave function tells you where a particle can be detected, and that can be in several places, but in the end it is only actually detected in only one of those places.
IshKebab 10y ago
They couldn't reliably detect single photons. Being able to see one in every thousand single photons would still count as being able to see them. Anyway there was an article on Ars recently about directly observing entanglement, so it's kind of already been done.
biswaroop 10y ago
A lot of the tests of single-photon entanglement require coincidence measurements: being able to detect if two photons arrived at the same time. I'm not sure how fast the human brain would be for these kinds of measurements. People usually use FPGA-based amplifiers with fast photodiodes.
tim333 10y ago
Yeah I was thinking cool, you could use cinema 3d specs for the polarizers and just need a source of entangled photons. The latter seems tricky though - all the sources I could find are infrared or lower frequency and so wouldn't be visible. Some info here http://physics.stackexchange.com/questions/172159/what-laser-and-bbo-are-needed-to-create-entangled-laser-streams http://physics.stackexchange.com/questions/172159/what-laser...

by IIAOPSW 10y ago

markcerqueira 10y ago

Just tried this experiment at home! Felt about one photon in my left eye and two in my right in one minute!! :D

nsxwolf 10y ago
What's your source of single photons?
- markcerqueira 10y ago
  Forgot the margin of error! +/- 2 photons!!! :D :D :D
- VLM 10y ago
  A quarter century ago we used a well characterized laser at a known power level that given a very precise wavelength and total power results in a very precise number of photons per second, like on the order of somethingE15 photons per second. From what I remember of filters neutral density transmission is log, so its pretty easy with a laser power meter to prove a ND2.0 outputs 1e-2 of input photons and turns the remainder of photons into heat or reflects them. Show an easily measurable somethingE15/sec photons out of a laser and the meter will read 1% power. Now you can buy neutral density filters of all kinds of measurable density. And filters stack, 1% of 1% is what you'd expect, not something crazy like average or RMS or whatever. So my numbers above might be all messed up but conceptually it boiled down to create a "normal scale human brightness" fountain of a knowable number of photons per second and filter it such that theoretically about one sneaks thru every second or once in awhile or whatever. Unfortunately we didn't have time to fool around with looking at it. From memory, I think we used it as some kind of quantum proof lab. So part one is diffraction patterns prove photons totally are definitely waves, and part two of the lab was this really sensitive photometer (essentially a geiger counter for photons) shows that each light photon is a distinct and countable bullet. And look, varying the density of the filter stack has no effect on the energy of each photon bullet it merely affects the rate at which they arrive isn't quantum mechanics spooky and wonderful? If that wasn't what we did with it, it probably should have been, or at least from memory I think that's pretty close to what we did. I suppose in the modern era lasers are a lot more powerful so you would need a better filter and rather than the weird vacuum tube photon sensor you'd just use a COTS solar panel and measure the single electrons produced by the single photons (within solar panel efficiency correction factor etc) You know whats really fun to do with quantum mechanics, is do a dual slit diffraction graph with a source that's like 1 photon per second so you know the apparatus only has one photon in flight at any given time. Rather than doing the two parts of my undergrad lab separately, do them together. In my infinite spare time that would be fun to build at home. I would imagine it would take a long time to gather the data, perfect for home amateur scientist types. I know what that graph looks like, and it freaks people out every time.
  - nsxwolf 10y ago
    I only understood a tiny bit of what you said, but I do get freaked out by the double slit experiment with single photons. It's like the photon is interfering with versions of itself in alternate universes.

Immortalin 10y ago

Can this be used for neutrino detection? Instead of ice + light sensor, you use sweatshop + human. Someone should do the math, perhaps in the right country it is cheaper to use mass indentured labor than electronics. (This is just a thought experiment, I am not supporting sweatshops)

flukus 10y ago
I think the mental pressures from confining people into completely dark rooms underground for hours on end might produce some false positives. Probably wouldn't tell us much about the characteristics of the light either.
- dalke 10y ago
  We've done it before. Geiger and Marsden were the first to observe what is now often called the Rutherford gold foil experiment, https://en.wikipedia.org/wiki/Geiger%E2%80%93Marsden_experiment https://en.wikipedia.org/wiki/Geiger%E2%80%93Marsden_experim... . They used a microscope to look at the flashes of fluorescent light created after the alpha particle scatters from the foil. (We could repeat this experiment in upper-level physics lab class. The teacher said it takes about 20 minutes for the eye to become sensitive enough to see flashes. He said then that the eye could see a single photon. Looking around now, I confirmed that papers of the time only said that was needed no more than 10 quanta.) So while there may be some false positives, it's not high enough to make it useless.
antognini 10y ago
I seem to remember doing a similar problem in an order of magnitude astrophysics class I took. We calculated that there were good odds that at least one person on the planet detected a neutrino from Tycho's supernova when it interacted with the vitreous body of the eyeball. (This is from memory, so don't quote me on it --- I may have remembered the sign wrong!)
Cerium 10y ago
This concept is explored in Neal Stephenson's Anathem. To avoid spoilers, I will be vague. One of the orders in the novel runs such an experiment. They have many people watching a pool or water or ice, and they independently record flashes they may see. If everyone sees the same thing, then they have captured a neutrino.

StanislavPetrov 10y ago

>We could literally see quantum mechanical behavior with our own eyes! That occurred to me as well as I read that article. It certainly raises some interesting questions about potential observations and wavefunction collapse.

noobermin 10y ago

Just to note, they do hint at that in the end of the article, so you bet your socks scientists are thinking about it. It certainly was one of the first thing that entered my mind.

grondilu 10y ago

If you see anything it would mean that the photon had been entangled with your retina, your visual nerve and your brain. All those being macroscopic objects, you could not see any quantum behavior. I'm not sure what would you expect to see anyway. A photon in two places at once? That's not how it works. The wave function tells you where a particle can be detected, and that can be in several places, but in the end it is only actually detected in only one of those places.

IshKebab 10y ago

They couldn't reliably detect single photons. Being able to see one in every thousand single photons would still count as being able to see them. Anyway there was an article on Ars recently about directly observing entanglement, so it's kind of already been done.

biswaroop 10y ago

A lot of the tests of single-photon entanglement require coincidence measurements: being able to detect if two photons arrived at the same time. I'm not sure how fast the human brain would be for these kinds of measurements. People usually use FPGA-based amplifiers with fast photodiodes.

tim333 10y ago

Yeah I was thinking cool, you could use cinema 3d specs for the polarizers and just need a source of entangled photons. The latter seems tricky though - all the sources I could find are infrared or lower frequency and so wouldn't be visible. Some info here http://physics.stackexchange.com/questions/172159/what-laser-and-bbo-are-needed-to-create-entangled-laser-streams http://physics.stackexchange.com/questions/172159/what-laser...