First-ever snapshot of the dual nature of light

March 2, 2015 10:58 AM

Scientists at the École Polytechnique Fédérale de Lausanne have captured "The first ever photograph of light as both a particle and wave" (images of the photo and the microscope in right hand column) using "EPFL’s ultrafast energy-filtered transmission electron microscope – one of the two in the world." The EPFL's explanatory video: Two-in-one photography: Light as wave and particle. Reference: Simultaneous observation of the quantization and the interference pattern of a plasmonic near-field. Nature Communications.
posted by cwest (23 comments total)

Pretty sure I was always taught that any measurement/disturbance of a photon ALWAYS forces it to manifest as one or the other, but never both, afterwards.

Are they over-promising? I'm not qualified to say. If so, though, bring on the physicist-types to refute this.
posted by ZenMasterThis at 11:03 AM on March 2, 2015 [1 favorite]

Looks white-and-gold to me.
posted by yoink at 11:07 AM on March 2, 2015 [22 favorites]

As it so happened, I had just finished listening to an In Our Time episode on Photons, when I clicked over to MeFi and saw this FPP.
I love nature-of-the-universe stuff like this.
posted by Thorzdad at 11:14 AM on March 2, 2015 [1 favorite]

Looks like a dirty beach.
posted by marxchivist at 11:15 AM on March 2, 2015

I'm finding that photo rather unsatisfying.
posted by DarkForest at 11:29 AM on March 2, 2015 [2 favorites]

The first ever photograph of light as both a particle and wave

And the next time Gilchrist's Light Can Be Both Wave and Particle gets reprinted I hope some enterprising editor chooses this for the cover design.
posted by octobersurprise at 11:30 AM on March 2, 2015

Pretty sure I was always taught that any measurement/disturbance of a photon ALWAYS forces it to manifest as one or the other, but never both, afterwards.

So what do we mean as "wave" and "particle"? The wave nature of light means that it doesn't have a distinct location before measurement, i.e. it is smeared out and can interfere with itself, creating waves. That happens before measurement occurs. The particle nature of light means that when you measure the number of photons at a given place, it has to be 0 or 1 or 2 or 3 or..., not some continuous variable.

This is a cool paper, but I'd argue that we've seen the simultaneous dual nature of light before, in single-photon double slit interferometry experiments.
posted by Maecenas at 11:31 AM on March 2, 2015 [3 favorites]

Where is the photograph? Is it the rainbow-y thing at the top of the article? Or is it somewhere in the cartoon video? I didn't watch it because it looked too silly. Is this a dumb question?
posted by Ratio at 11:39 AM on March 2, 2015 [1 favorite]

So what do we mean as "wave" and "particle"?

And what do we mean by "photograph"? This is just a graphical representation of experimental results, isn't it? It's not something produced by direct "exposure" of a sensitive medium to light. Or am I missing something?
posted by yoink at 11:39 AM on March 2, 2015 [1 favorite]

I'm finding that photo rather unsatisfying.

This is cool, but it seems less like a photograph and more like a false-colored computer rendering. A graph of photons is different than a photograph. Calling it the latter is somewhat misleading.
posted by tempestuoso at 11:40 AM on March 2, 2015 [2 favorites]

And the next time Gilchrist's Light Can Be Both Wave and Particle gets reprinted I hope some enterprising editor chooses this for the cover design.

Or the album art for an EDM version of Unknown Pleasures.
posted by Ratio at 11:43 AM on March 2, 2015 [2 favorites]

A graph of photons is different than a photograph.

Well played, sir. For one thing, you'll never spend your life just wishing over a graph of photons.
posted by GenjiandProust at 11:55 AM on March 2, 2015 [3 favorites]

Ratio: " EDM version of Unknown Pleasures."

Don't you ever ever ever put those two terms next to each other.

---

That said, I am a little confused. It does look like, instead of shining light at another entity (i.e. electron) which causes disturbance, and thus, is why you have the Heisenberg uncertainty (the energy knocks the electron. the more precise measurement you get, the more energy you use, the more it gets knocked out of place, the less you can say about its momentum(?))... They're creating a standing wave, and then, IIRC (I read the article earlier today, so I may be remembering wrong, and I'm too lazy to go check now), shooting electrons at the standing photon wave, which they claim then produces the particle image.

Look forward to some physicist (physicsmattsignal! or any others who work in the field, as I know there are some others here) explaining better.

I want to discount this, but obviously, this is done by world class researchers, and is some sort of effect, and I'm just some chump who reads popular books on science so I wouldn't dare try to argue the case that what they're claiming isn't true, but it would be nice to know how this actually works...
posted by symbioid at 11:56 AM on March 2, 2015

it seems less like a photograph and more like a false-colored computer rendering

I don't mind that. I'm just not getting any sense of particle out of it. It makes me think of a visual representation of a probability wave.
disclaimer: I don't know that much about physics beyond what you get in mainstream science writing.
posted by DarkForest at 11:57 AM on March 2, 2015

Some of you might like the movies linked for download in the Nature article's supplementary information section.
posted by barchan at 11:57 AM on March 2, 2015 [1 favorite]

Don't you ever ever ever put those two terms next to each other.

I agree, but in the right hands it could be glorious.
posted by Ratio at 11:58 AM on March 2, 2015

It's not a one or the other thing. It's a continuum. We would be better off dropping this misguided linguistic notation.
posted by edd at 2:18 PM on March 2, 2015

Hmm. According to the picture, light is some kind of Velcro.
posted by sexyrobot at 2:23 PM on March 2, 2015

I am not a physicist, but while I'm sure this is a nice paper, the press release is silly:
- It's not a photograph, it's a chart of stuff;
- It's not "of" light, it's of the interaction of electrons with surface plasmon polaritons, which are quasi-particles that act like quantum-mechanical particles but aren't actually. They're just convenient ways of describing the behavior of light interacting with oscillating electrons in a conductor. As far as I can make out they're like the "holes" people talk about with semiconductors: nobody is claiming a hole is a thing, but it's useful to pretend that it's a positive charge carrier that's like an anti-electron.

As a layperson, I tried to make some sense of the paper. The relevant paragraph is this AFAICT:

In the present work, an SPP standing wave is photoinduced on an isolated metallic nanowire using an intense fs laser pulse, and the ability to control its spatial interference pattern is demonstrated by tuning the polarization of the excitation light. A snapshot of the interaction between the imaging electrons and the SPP standing wave is taken using a new ultrafast-imaging methodology that utilizes an electron imaging filter to form a two-dimensional (2D) projection of one spatial coordinate versus electron energy. These energy-space-resolved images simultaneously yield both the quantization of the photoinduced SPP field and its characteristic FP interference pattern, given by the one-dimensional (1D) confinement of the single nanowire.

The three dimensions in the picture aren't all spacial; they're distance (along the wire); energy level; and density of electrons. So this isn't really a picture.

Based on the electrons they shoot near the wire, they can compute where the most energetic spots on the wire must be. The energy distribution in space looks like a standing wave thus indicating the wavy nature of the polaritons, but the energy *levels* are quantized, thus indicating the particle nature of the polaritons.

That's pretty cool! Quantized and wavy at the same time! But science press releases continue to be silly.
posted by goingonit at 2:33 PM on March 2, 2015 [5 favorites]

This only barely makes sense with the supplemental videos barchan linked to. But I am unclear where the polarization angles are coming from. This is a component of the input laser light, and they are varying it continuously to generate the output graphs?
posted by charlie don't surf at 4:13 PM on March 2, 2015

So, if I'm reading that image right, light is a particle, a wave, and multicolored bubble-wrap.

Honestly, I always sort of suspected...
posted by quin at 8:38 PM on March 2, 2015 [1 favorite]

edd: It's not a one or the other thing. It's a continuum. We would be better off dropping this misguided linguistic notation.

I both agree and disagree, strenuously.

It's not a continuum. The quantum nature of photons doesn't extend in any way towards a "continuum". There's no way to ever have 1.001 photons.

But the linguistic notation of this duality is confusing - it's a bit like the Mystery of the Trinity, only for physicists (, optical engineers, and some electrical engineers). One thing has two, apparently contradictory natures about it.

I think of it more like the real/imaginary axes (not saying this literally, but by analogy). The wave (imaginary) nature of light generally exhibits when the particle (real) nature is at an ebb, and to measure its full wave potential requires us to abandon the quantum count nature. The two certainly both "exist", but cannot both be measured at the same time. (Now, I'm not suggesting there's a cyclical component to this duality - I'm just saying the two behave like tied, orthogonal axes.)
posted by IAmBroom at 2:25 PM on March 3, 2015

goingonit: I am not a physicist, but ...

... you still did a damn good job of it. Take up science reporting, please?
posted by IAmBroom at 2:28 PM on March 3, 2015