8 ms·

Newly observed optical state could enable quantum computing with photons

111 points by charlysl 9y ago

a3n 9y ago
> While photons normally have no mass and travel at 300,000 kilometers per second (the speed of light), the researchers found that the bound photons actually acquired a fraction of an electron’s mass. These newly weighed-down light particles were also relatively sluggish, traveling about 100,000 times slower than normal noninteracting photons. 300,000 / 100,000 = 3 "Relatively sluggish?" That seems more like profoundly sluggish, for light.
- ghusbands 9y ago
  3km/s is not sluggish and certainly not profoundly so. But it is relatively sluggish, compared to light. The choice of wording is fine.
  - gutnor 9y ago
    Is "relatively sluggish" the proper wording for "5 order of magnitude slower" ? The overnight backup was relatively sluggish last night, instead of 1 minute we expect it to take a little over 2 months.
    - mort96 9y ago
      I mean, in relation to all everyday objects, 3 kilometers per second is stupidly fast and not at all sluggish. The overnight backup was relatively sluggish last night, instead of 1 microsecond it took a little over 100 milliseconds.
    - ghusbands 9y ago
      Relatively is a modifier that here means "compared to something else". When someone says "relatively X", they are saying it is not actually "X" but it seems so in comparison. So they are saying that the combined particle isn't sluggish (because 3km/s is very much faster than a slug), but in comparison to light it _is_ sluggish. Hence, relatively sluggish.
      - TomMarius 9y ago
        Why is this downvoted?
- kurthr 9y ago
  An index of refraction of 3 is relatively high (like silicon carbide). Glass and a lot of optically transparent materials are only ~1.5. But, if you look at IR transparent materials like silicon, gallium arsenide, or germanium, you can get up to and over 4. More to the point, diode pumped solid state lasers are a common thing these days so photons interacting just isn't news... (edit) however if (and I can't tell without reading the original paper) it is actually the effect of photon mass (eg due to light density) on the photons itself, then it's a significant technical achievement! Just not how I'd have phrased it to a technical audience.
  - kgwgk 9y ago
    This is more like an index of refraction of 100000, isn't it?
gmueckl 9y ago
Is anyone else annoyed by the fact that while MIT news is good at creating interest in their stories, they are annoyingly watered down and never link back to the source paper they are paraphrasing? In this instance, they never mention the paper title even once.
- smoyer 9y ago
  And they tend to over-generalize - "While photons normally have no mass and travel at 300,000 kilometers per second (the speed of light)". The maximum speed of a photon is (currently?) around 300,000 kps but they often travel slower than this. Our fiber optics systems are coursing with photons that travel approximately 200,000 kps. The key results of this experiment is that the photons are interacting with each other ... and that they acquire mass. The flashlight analogy is actually one that I not only described to people, but built a unique product around in the '90s. CyberFiber (yeah ... it was an tongue-in-cheek name for an engineering project that escaped into the marketing and sales department) was a duplex communication platform that used the same wave-length of light for both directions. It was a great marketing tool but required that your optical connections had very low reflectivity (and nobody likes to put coupling gel in their connectors).
  - comboy 9y ago
    Photons travelling through fiber are still traveling at 300,000 km/s. It's just that they bounce of walls making their path longer and much more importantly than that, the medium is denser. Speed of light through glass is ~2e5 km/s, but photons are still travelling at 3e5 km/s. It's just that they hit atoms, energy gets absorbed and re emitted and so on. But photons always move at 3e5 km/s. The speed of light, that is the speed of a photon, is a constant.
    - mjburgess 9y ago
      That's not correct, but a widely held view. The speed differs to the properties of the EM field in these materials, not due to absorption.
amelius 9y ago
Does this have implications for Maxwell's equations?
- gus_massa 9y ago
  No, no changes to Maxell's equation, but I think it's easy to be mislead by the bad press coverage and title. They only made a weird material where photons interact in a strange way, the photons "like" to be bound in triplets in that material. There are other unusual materials, for example one special crystal can split a green photon into two infrared photons. Or the inverse, pick two photons and create a green photon with them. https://en.wikipedia.org/wiki/Spontaneous_parametric_down-conversion https://en.wikipedia.org/wiki/Spontaneous_parametric_down-co... The process in the article is different because it's temporal and it's only inside the material, but the split/unsplit make new photons than can live forever outside the material. (There are other differences ...) Maxwell's Equation is only valid in vacuum, or when the material doesn't do anything interesting. The technical term is probably "linear materials". In nonlinear materials, weird things can happened and you can no long use the Maxwell's Equations.
  - gmueckl 9y ago
    I never got into nonlinear optics deeply. But I always thought that the nonlinear effects like frequency shifting work with the ordinary Maxwell equations, but with nonlinear material equations that have higher orders of susceptibility and permittivity in them.
  - John_KZ 9y ago
    I came here to say that. I'm no expert in optics, much less quantum optics, but they seem to have created some kind of fancy material with unusual optical properties. I'm very disappointed that MIT News themselves are so misleading. If I couldn't pirate the paper, I'd be left with the impression that they said they broke some kind of fundamental physics rule. They should leave heavy editorialization and sensationalisation for the news websites further down the chain.
    - 9y ago
ghusbands 9y ago
The paper is "Observation of three-photon bound states in a quantum nonlinear medium"; details here: http://science.sciencemag.org/content/359/6377/783 http://science.sciencemag.org/content/359/6377/783
- danielam 9y ago
  Discussion here: https://news.ycombinator.com/item?id=16392892 https://news.ycombinator.com/item?id=16392892 Edit: Previous submission, not discussion.
  - dhimes 9y ago
    There's actually no discussion there.
jadavies 9y ago
I really, really hoped that they'd at last confirmed the existance of octarine :)
sbg123 9y ago
Create? Really? (Discover surely)
deleted 9y ago
[deleted]
Jeff_Brown 9y ago
"A photon’s phase indicates its frequency of oscillation." That can't be right. Phase and frequency are orthogonal.
- hpcjoe 9y ago
  Yeah, there were some serious faulty elements of the article. That was just one. Apart from that, I'm not aware of experiments that measure absolute phase, only relative phase differences. But I've been out of physics for 20+ years, so mebbe they've gone and done it.
Koshkin 9y ago
TL;DR: entanglement of photons
bawana 9y ago
Please clarify the model that describe the mechanism of the observations. Is it A) a photon travels through a medium and changes the state of an atom in some way. Another photon travels through the medium and interacts with the same ‘excited’ atom. The second photon is then changed in a way directly related to the first photon Or B) a photon interacts with an atom but instead of being absorbed and retransmitted, it is just absorbed and captured. Only when another photon is captured does the atom release them both. In A the information from the first photon is stored in the atom (flipped spin of an electron or proton for example) but the total energy of the atom is not changed much. In B, the energy of the photon is contained in the atom (jump of an electron to a higher energy orbital) and the atom is truly in an excited state- this would be the mechanism of laser. An incident photon would then push the excited atom to quantum orgasm where it would spew out its photons. I tend to favor B because it might make me famous as the inventor of the ‘quantum orgasm’.
- whatshisface 9y ago
  B is called stimulated emission and is the principle behind lasers.
crispycrafter 9y ago
Just trying to wrap my head around this. Photon energies are distributed across quantised states. We can obtain the single photon energy for a given wave-length by the Planck-Einstein relation. We then assume the photons become "entangled", and decrease their speed. Is this to conserve momentum/energy, assuming the frequency is unaltered. I assume this frequency stays the same on the premise of constructive interference, and hence not altering the phase or frequency.

111 points by charlysl 9y ago

a3n 9y ago

> While photons normally have no mass and travel at 300,000 kilometers per second (the speed of light), the researchers found that the bound photons actually acquired a fraction of an electron’s mass. These newly weighed-down light particles were also relatively sluggish, traveling about 100,000 times slower than normal noninteracting photons. 300,000 / 100,000 = 3 "Relatively sluggish?" That seems more like profoundly sluggish, for light.

ghusbands 9y ago
3km/s is not sluggish and certainly not profoundly so. But it is relatively sluggish, compared to light. The choice of wording is fine.
- gutnor 9y ago
  Is "relatively sluggish" the proper wording for "5 order of magnitude slower" ? The overnight backup was relatively sluggish last night, instead of 1 minute we expect it to take a little over 2 months.
  - mort96 9y ago
    I mean, in relation to all everyday objects, 3 kilometers per second is stupidly fast and not at all sluggish. The overnight backup was relatively sluggish last night, instead of 1 microsecond it took a little over 100 milliseconds.
  - ghusbands 9y ago
    Relatively is a modifier that here means "compared to something else". When someone says "relatively X", they are saying it is not actually "X" but it seems so in comparison. So they are saying that the combined particle isn't sluggish (because 3km/s is very much faster than a slug), but in comparison to light it _is_ sluggish. Hence, relatively sluggish.
    - TomMarius 9y ago
      Why is this downvoted?
kurthr 9y ago
An index of refraction of 3 is relatively high (like silicon carbide). Glass and a lot of optically transparent materials are only ~1.5. But, if you look at IR transparent materials like silicon, gallium arsenide, or germanium, you can get up to and over 4. More to the point, diode pumped solid state lasers are a common thing these days so photons interacting just isn't news... (edit) however if (and I can't tell without reading the original paper) it is actually the effect of photon mass (eg due to light density) on the photons itself, then it's a significant technical achievement! Just not how I'd have phrased it to a technical audience.
- kgwgk 9y ago
  This is more like an index of refraction of 100000, isn't it?

gmueckl 9y ago

Is anyone else annoyed by the fact that while MIT news is good at creating interest in their stories, they are annoyingly watered down and never link back to the source paper they are paraphrasing? In this instance, they never mention the paper title even once.

smoyer 9y ago
And they tend to over-generalize - "While photons normally have no mass and travel at 300,000 kilometers per second (the speed of light)". The maximum speed of a photon is (currently?) around 300,000 kps but they often travel slower than this. Our fiber optics systems are coursing with photons that travel approximately 200,000 kps. The key results of this experiment is that the photons are interacting with each other ... and that they acquire mass. The flashlight analogy is actually one that I not only described to people, but built a unique product around in the '90s. CyberFiber (yeah ... it was an tongue-in-cheek name for an engineering project that escaped into the marketing and sales department) was a duplex communication platform that used the same wave-length of light for both directions. It was a great marketing tool but required that your optical connections had very low reflectivity (and nobody likes to put coupling gel in their connectors).
- comboy 9y ago
  Photons travelling through fiber are still traveling at 300,000 km/s. It's just that they bounce of walls making their path longer and much more importantly than that, the medium is denser. Speed of light through glass is ~2e5 km/s, but photons are still travelling at 3e5 km/s. It's just that they hit atoms, energy gets absorbed and re emitted and so on. But photons always move at 3e5 km/s. The speed of light, that is the speed of a photon, is a constant.
  - mjburgess 9y ago
    That's not correct, but a widely held view. The speed differs to the properties of the EM field in these materials, not due to absorption.

amelius 9y ago

Does this have implications for Maxwell's equations?

gus_massa 9y ago
No, no changes to Maxell's equation, but I think it's easy to be mislead by the bad press coverage and title. They only made a weird material where photons interact in a strange way, the photons "like" to be bound in triplets in that material. There are other unusual materials, for example one special crystal can split a green photon into two infrared photons. Or the inverse, pick two photons and create a green photon with them. https://en.wikipedia.org/wiki/Spontaneous_parametric_down-conversion https://en.wikipedia.org/wiki/Spontaneous_parametric_down-co... The process in the article is different because it's temporal and it's only inside the material, but the split/unsplit make new photons than can live forever outside the material. (There are other differences ...) Maxwell's Equation is only valid in vacuum, or when the material doesn't do anything interesting. The technical term is probably "linear materials". In nonlinear materials, weird things can happened and you can no long use the Maxwell's Equations.
- gmueckl 9y ago
  I never got into nonlinear optics deeply. But I always thought that the nonlinear effects like frequency shifting work with the ordinary Maxwell equations, but with nonlinear material equations that have higher orders of susceptibility and permittivity in them.
- John_KZ 9y ago
  I came here to say that. I'm no expert in optics, much less quantum optics, but they seem to have created some kind of fancy material with unusual optical properties. I'm very disappointed that MIT News themselves are so misleading. If I couldn't pirate the paper, I'd be left with the impression that they said they broke some kind of fundamental physics rule. They should leave heavy editorialization and sensationalisation for the news websites further down the chain.
  - 9y ago

ghusbands 9y ago

The paper is "Observation of three-photon bound states in a quantum nonlinear medium"; details here: http://science.sciencemag.org/content/359/6377/783 http://science.sciencemag.org/content/359/6377/783

danielam 9y ago
Discussion here: https://news.ycombinator.com/item?id=16392892 https://news.ycombinator.com/item?id=16392892 Edit: Previous submission, not discussion.
- dhimes 9y ago
  There's actually no discussion there.

jadavies 9y ago

I really, really hoped that they'd at last confirmed the existance of octarine :)

sbg123 9y ago

Create? Really? (Discover surely)

deleted 9y ago

[deleted]

Jeff_Brown 9y ago

"A photon’s phase indicates its frequency of oscillation." That can't be right. Phase and frequency are orthogonal.

hpcjoe 9y ago
Yeah, there were some serious faulty elements of the article. That was just one. Apart from that, I'm not aware of experiments that measure absolute phase, only relative phase differences. But I've been out of physics for 20+ years, so mebbe they've gone and done it.

Koshkin 9y ago

TL;DR: entanglement of photons

bawana 9y ago

Please clarify the model that describe the mechanism of the observations. Is it A) a photon travels through a medium and changes the state of an atom in some way. Another photon travels through the medium and interacts with the same ‘excited’ atom. The second photon is then changed in a way directly related to the first photon Or B) a photon interacts with an atom but instead of being absorbed and retransmitted, it is just absorbed and captured. Only when another photon is captured does the atom release them both. In A the information from the first photon is stored in the atom (flipped spin of an electron or proton for example) but the total energy of the atom is not changed much. In B, the energy of the photon is contained in the atom (jump of an electron to a higher energy orbital) and the atom is truly in an excited state- this would be the mechanism of laser. An incident photon would then push the excited atom to quantum orgasm where it would spew out its photons. I tend to favor B because it might make me famous as the inventor of the ‘quantum orgasm’.

whatshisface 9y ago
B is called stimulated emission and is the principle behind lasers.

crispycrafter 9y ago

Just trying to wrap my head around this. Photon energies are distributed across quantised states. We can obtain the single photon energy for a given wave-length by the Planck-Einstein relation. We then assume the photons become "entangled", and decrease their speed. Is this to conserve momentum/energy, assuming the frequency is unaltered. I assume this frequency stays the same on the premise of constructive interference, and hence not altering the phase or frequency.