Photo First: Light Captured As Both Particle and Wave

mpicpp sends word that scientists have succeeded in capturing the first-ever snapshot of the dual behavior of light. "It's one of those enduring Zen koans of science that we've all grown up with: Light behaves as both a particle and a wave—at the same time. Einstein taught us that, so we're all generally on board, but to actually understand what it means would require several Ph.D.s and a thorough understanding of quantum physics. What's more, scientists have never been able to devise an experiment that documents light behaving as both a wave and a particle simultaneously. Until now. That's the contention of a team of Swiss and American researchers, who say they've succeeded in capturing the first-ever snapshot of light's dual behavior. Using an advanced electron microscope – one of only two on the planet – at the EPFL labs in Switzerland, the team has generated a kind of quantum photograph of light behaving as both a particle and a wave. The experiment involves firing laser light at a microscopic metallic nanowire, causing light to travel — as a wave — back and forth along the wire. When waves traveling in opposite directions meet, they form a "standing wave" that emits light itself — as particles. By shooting a stream of electrons close to the nanowire, the researchers were able to capture an image that simultaneously demonstrates both the wave-nature and particle-nature of light. 'This experiment demonstrates that, for the first time ever, we can film quantum mechanics — and its paradoxical nature — directly,' says lead researcher Fabrizio Carbone of EPFL, on the lab's project page. The study is to be officially published this week in the journal Nature Communications."

Comments

not the first time

[ralphsiegler]

every dual slit experiment shows light behaving as both particle and wave, because every photon only interferes with itself. Two or more photons never interfere with each other.

Re:not the first time

[stoborrobots]

The wave-particle duality is not a quantum superposition like you're describing (which would break down under measurement), although the caricatured manner in which we teach it might lead you believe that. It's a little more simple than that.

In our world, we are used to two kinds of things: particles, and waves. We are used to this distinction, and describe most things in one of these manners. Sound is a wave, a billiard ball is a particle, vibrations are waves, bricks are particles. If something is a particle, it has certain properties, like position, size, and shape. If it is a wave, it has certain other properties like wavelength, frequency, and amplitude. In addition, there are some common properties like velocity and direction.

When it came to studying light (and many other quantum stuffs), we can't directly see what it's made of. But we can take measurements of each "puff" of light, and infer its properties that way. When we do this, we notice that puffs of light have some properties which are particle-like, and some which are wave-like. So the term "particle-wave duality" became popular to describe this new material that was behaving simultaneously like a particle and a wave. It doesn't make sense to ask which one it is - a "puff" of light is neither a particle, nor a wave, but a different kind of stuff which has some properties of each.

It's the measurement

[thebes]

If you attempt to measure it in the way you would measure a wave, it will present itself as a wave.

If you attempt to measure it in the way you would measure a particle, it will present itself as a particle.

Light doesn't choose to be a particle or a wave at any given time, the measurement we use defines the characteristics it has. Nothing more, nothing less.

Re:It's the measurement

[Anonymous Coward]

I wish physicists would stop using the word "measurement" when talking about quantum mechanics. To detect fundamental particles we have to interact with them in an intrusive or destructive way. It's not like putting a rock on a scale to measure its weight or putting a ruler to a golf ball. We don't get to keep the original particle after we're done. It's more like colliding snowballs with other snowballs to probe their properties. You destroy or transform them in the process. If this was how we conveyed the concepts, the quantum ideas would become a lot more understandable.

3-D to 2-D display

[Camel Pilot]

From the fine article it provides a caption to the graphic

"The bottom "slice" of the image shows the particles, while the top image shows light as a wave""

Looking at the graphic the top image is a 3-D display and the bottom just a color coded 2-D representation with topo lines. I see nothing in this displaying the wave aspect and particle aspect. Mistake?

Re:My brain is full

[youngone]

There's no way of doing that. Feynman said "I think I can safely say that nobody understands quantum mechanics". You've probably got no chance. :-)

Several Ph.D.s?

[TechyImmigrant]

> but to actually understand what it means would require several Ph.D.s and a thorough understanding of quantum physics

No, just some understanding of statistics and calculus up to tensors along with an ability to know why you know something rather than just knowing things.

When we make out relatively simple things (like quantum physics) to be complex, when in fact they are just strange we do a disservice to those who might otherwise put in the effort to understand.

This attitude pisses me off

[crioca]

Light behaves as both a particle and a wave—at the same time. Einstein taught us that, so we're all generally on board, but to actually understand what it means would require several Ph.D.s and a thorough understanding of quantum physics

Stop pretending physics is spooooky. It's not that difficult to understand, at least at a superficial level. And I don't have a degree, let a lone a Ph.D, but even I can explain it (again, superficially):

Time dilation means that the faster you go, the slower time goes. If you're travelling at the speed of light in a vacuum, then the speed at which you're travelling through time is slowed infinitely. This means a photon experiences no passing of time between the moment it is created, and the moment it collides with something.

But the speed of light is finite, so it has to travel through time to go between two points. But because from the photon's perspective it's travel is instantaneous, it can't experience that time. So a photon doesn't know where it's going to land, until it does. And so until it does land, it could have landed anywhere. So when a photon is created, it travels out in all directions, like a wave, until it lands somewhere and the wave collapses.

The part that's hard to understand is the why.