Friday, March 13, 2015

195.9 - And Another Thing: researchers make quantum photograph of light as simultaneously wave and particles

And Another Thing: researchers make quantum photograph of light as simultaneously wave and particles

Last for this week, another reach into the pile labeled And Another Thing.

All right, here's the deal. The argument that had gone on in science for a few hundred years about whether light is a wave or stream of particles was solved by Einstein: It's both, simultaneously.

This also meant in practice that if you looked at light as if it were a wave, you detected it as a wave. If you looked at it like it was a stream of particles, called photons, you detected it as a stream of particles. What you got depended on how you looked at it. In a way, it's like trying to describe how you see a piece of paper: It will depend on whether you are looking at it broadside on or edge-on; both are accurate descriptions of the same paper, but will still be considerably different.

But here's the problem: If light is both particles and a wave, how can you see it as both at the same time? You would think you should be able to since it is both, but how can you do that if how you see it depends on how you look at it? How can you see the broadside view and the edge-on view of the paper at the same time?

A team of Swiss and American researchers at the EPFL labs in Switzerland say they have overcome the problem. Using an advanced electron microscope - one of only two of that type on the planet - the team has generated a kind of quantum photograph of light behaving as both a particle and a wave.

First, the team fired laser light at an extremely thin wire and created a standing wave. You know what that is: Think of having a rope secured at one end and you flip the free end, sending a wave down the rope which bounces back from the secured end. But if you keep flipping in the correct rhythm, you can set up a pattern where the waves in the rope don't move along it but just go up and down. That's a standing wave.

Okay, having done that, the researchers then fired a stream of electrons very close to the wire, so close that the electrons interacted with the photons, that is, the particles of light, causing a transfer of energy that would case the particles to either speed up or slow down. That change can be detected and measured.

Then all you have to do is "take a picture" - which in this case is a lot more complicated than whipping out your iPhone and involves a lot of mathematical reconstruction, but the idea of "getting an image" is pretty much the same.

The result is what you see in the illustration: the world's first photo showing light behaving as both a wave and a particle. The wave depiction is at the top, and the bottom slice shows the photons.

And if you don't think that's cool, there is no hope for you.

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