First photograph of light as both a particle and wave (2015) | Hacker News Reader

First photograph of light as both a particle and wave (2015)

m.phys.org

139 pointsThomPete37 comments

This article is much more clear on what the image actually represents: http://www.livescience.com/50019-image-light-wave-particle.h...

"A clever technique and an ultrafast electron microscope have caught an image of light behaving as both particle and wave at the same time. Here, the wave nature is demonstrated in the wavy upper portion, while the particle behavior is revealed below, in the outlines showing energy quantization."

Credit: Fabrizio Carbone/EPFL

Also, this was all published on March 2, 2015.

It took me a few reads for this to sink in.

Quantum interference causes standing waves. Electron-photon particle collisions cause detectable energy release. The particle collisions occur in an interference pattern.

Yes, and the colors describe the speeds of the particles as a result of tbe electron-photon collisions.

It's not necessarily the particles we're seeing, just the particle behaviors from their collisions.

Swiss here. The École Polytechnique Fédérale de Lausanne (EPFL), where this experiment has been carried out, is one of the two federal institutes of technology, the other one is the Eidgenössische Technische Hochschule Zürich (ETHZ).

https://en.wikipedia.org/wiki/%C3%89cole_Polytechnique_F%C3%... https://en.wikipedia.org/wiki/ETH_Zurich

It didn't explain the picture.

Yeah, I don't know how to interpret it. It's not immediately obvious to me that I'm looking at a wave and particles at the same time.

Nor does it appear to be a photograph. It looks very much like a 3D rendering with false coloring.

Your eyes don't have quantum energy packet receptors :-) A normal photograph is made by bouncing light off something and detecting it. If you are using a CCD, you are still using false colour. It just happens to correspond to the true colour.

In this experiment, the electrons interact with the photons to produce quantum energy packets, which the microscope detects. What is the colour of the quantum energy packets? The question has no meaning, because they aren't light. Since the colour is arbitrary, they can choose to colour it in any way they find useful.

Having said that, I also don't understand the "photograph".

> Your eyes don't have quantum energy packet receptors

Actually, we do, so long as that energy is in the form of photons [1].

[1] http://www.nature.com/news/people-can-sense-single-photons-1...

> so long as that energy is in the form of photons

Of a particular range of frequencies

What the image represents is the energy loss/gain of a whole bunch of electrons that interact one at a time with a light wave traveling along a tiny metal wire (we call this kind of captive light wave a "phonon").

For each electron fired at the wire, it can either pass through unscathed, or it can interact with an electron and scatter off with a different energy, like two billiard balls hitting each other. The collision is fundamentally a collision between two particles. However, the fact that the properties of the collisions vary sinusoidally along the length of the wire imply that the photon is also acting like a wave oscillating up and down the wire.

I disagree that this is the "first time" that we've observed simultaneous wave-particle behavior, you can see the same thing by firing photons at two narrowly-placed slits. This results in a diffraction pattern as if the photons were interfering like waves, but we can confirm that we're detecting single photons at the detector, and you can even confirm that each photon travels through one slit or the other ... See https://en.wikipedia.org/wiki/Double-slit_experiment

One nit: A phonon is a vibration of a lattice, not light.

Yep, that should have said "plasmon". I messed up all of my comments on this thread. A plasmon isn't technically light either, it's an oscillation of the electric field in a conductor -- but it has wave/particle duality like a photon.

It's hard to grasp what was really captured on that image, but this still doesn't rule out the pilot wave theory. I think it's misleading to call it a photograph of light "as both a particle and wave".

I have a question about QM, which perhaps somebody here can answer: Is quantization an inherent property of the photon, or is it a property of the material (or of the interaction with it)?

If I remember correctly, quantisation occurs because of the solutions to certain differential equations in the geometry (eg of an atom, of a lasing chamber, etc).

The quantised states are the different solutions to that equation (the different energy levels + spin states in an atom.) - this holds for electrons in atoms being quantised.

The photoelectric effect, which has to do with incident photons, showed that you can't turn up the intensity of long wavelength light and ping electrons off things: the power input didn't change things, but a very low power of short wavelength photons did. Thus, Einstein concluded that there must be something specific about the energy of individual particles, not just the total energy stored in a wave. So it is observed in an interaction, but the information defining the final effect travels with the photon.

The equations describe reality, they don't form it (so far as we know!).

s/occurs because/can be deduced from/

I believe that the quantization of the photon is directly related to the idea the electrons can only move between discrete energy levels in their respective atoms.

The other answers posted here are not quite right. Light energy is indeed inherently quantized, and a photon is one quantum of light. In other words, you can't have a half-photon of light, only even multiples.

Einstein wrote the equation "E = h*(nu)", where h is the so-called "Planck's constant", and nu is the frequency of light. Translated, this means that each photon carries an amount of energy proportional to its frequency, higher-frequency photons (IR -> red -> blue -> UV -> X-ray) carry more energy.

tl;dr: Quantization is an inherent property of light.

Do you mean "whole" multiples?

Yes, integer multiples would be better. Don't know why I said even.

E=h*nu was derived by Max Planck, not Einstein.

Doh. Typing too fast. Thanks for the correction.

> E = h*(nu)

Yes, but the question is whether that is due to the material not being able to produce non-quantized photons. Stated differently, suppose we had a different way of generating photons, then could we theoretically create them in a non-quantized way?

Yep. They called "radiowaves".

Sounds logical, but then again, how fundamental is the "Q" in "QM"?

Extremely. Broken quanta will release its energy. Check solitons (example: https://www.youtube.com/watch?v=JD32kkoFU3Y ). Soliton wave can cross ocean, but if you broke it pattern, you will have regular waves, not a half of solition.

No, radio waves are also made up of photons that obey the same equation.

The best example I can come up with is Compton scattering. Here, you are colliding photons with an unbound particle, therefore one that does not have quantum energy states. The quantum nature of light is shown by the fact that the degree of scattering depends upon the energy (and therefore wavelength) of the incident photon, and not on the intensity. If light were just a wave, then the effect would go away if the intensity were low enough.

I don't think this is right. The energy of a photon is h multiplied by the frequency, but the frequency itself can be anything. Even if the process creating the photon is inherently quantized (e.g. bound electron with quantized energy levels), we will measure slightly different frequencies (and so different energies), due for example to the Doppler effect[1]. Still with the Doppler effect, you can give a photon an arbitrary frequency (energy) by changing the velocity of the reference frame where you make the measurement (that is, until someone shows that the velocity of the reference frame is quantized... not something that is presently known).

[1] https://en.wikipedia.org/wiki/Doppler_broadening

Yes, that's correct. This does not mean that the energy levels of light (more generally, EM radiation) are quantized -- photons can have any energy level. What it means is that, for light of a given frequency, you can deposit energy only in units of h(nu).

The quantization of light shows up in how it interacts with particles -- even unbound particles like free electrons, which also do not have quantized energy levels. Specifically, if light were NOT quantized, you could get the same effect with more intense light that you get with more energetic light. Instead, experiments show again and again that longer-wavelength light at high intensity gives a totally different effect from short-wavelength light at low intensity. Postulating that light consists of particles (photons) with E = h(nu) explains this difference.

This is really cool! What's the reason for the blue & violet colors to be raised more than others in the wave?

Is it just the timing of the snapshot? As in, another picture might show another color at the top of the wave? Or is the standing wave "stuck" in that position?

That's just the color scale they've used for the z axis.

https://www.eurekalert.org/pub_releases/2015-03/epfd-tfe0301...

> an exchange of energy "packets" (quanta) between electrons and photons

I thought that photons are the energy quanta (that electrons can absorb or lose).

Darn the ambiguous english language, do they mean the photograph is a particle-wave? because that wouldn't be a first. /s

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