Laser Creates Quantum Whirlpool

Quantus347 writes: Physicists at The Australian National Univ. (ANU) have engineered a spiral laser beam and used it to create a whirlpool of hybrid light-matter particles called polaritons. Polaritons are hybrid particles that have properties of both matter and light. The ability to control polariton flows in this way could aid the development of completely novel technology to link conventional electronics with new laser- and fiber-based technologies. Polaritons form in semiconductors when laser light interacts with electrons and holes (positively charged vacancies) so strongly that it is no longer possible to distinguish light from matter.

Comments

What, no Lightsaber jokes?

[Marxist Hacker 42]

Did I get first post?

Still, something tells me this is only a quantum effect, not macro

Re:What, no Lightsaber jokes?

[Anonymous Coward]

No light saber jokes. But I suspect that Deepak Chopra will put this in his next book.

Re: What, no Lightsaber jokes?

[Anonymous Coward]

Holodeck???

Re:What, no Lightsaber jokes?

[Anonymous Coward]

No, but I can't wait for the jokes about reversing the neutrality of the polariton flow.

Re:What, no Lightsaber jokes?

[michelcolman]

Watch out for the sharks in the quantum whirlpool. They love friggin lasers, apparently.

I thought the distinction was arbitrary already

[i kan reed]

Polaritons form in semiconductors when laser light interacts with electrons and holes (positively charged vacancies) so strongly that it is no longer possible to distinguish light from matter.

I thought the distinctions made already are already mostly ones of convenience and scale: matter is slow and heavy enough to mostly be possible to model as point masses, while light is fast, light, and numerous enough to be more convenient to treat as non-discrete energy than as individual photons.

Re:I thought the distinction was arbitrary already

[students]

Matter has mass. Light has no mass. That's a pretty significant distinction. A polariton's mass can change continuously as a function of energy from zero to about twice the electron mass.

The summary is a little odd. A hole is not a charged vacancy. A vacancy typically refers to a fixed (at low temperatures) location where an atom is missing in the lattice of a crystal. A hole is a mobile positive charge with mass similar to the electron mass.

(Recently finished my PhD studying polaritons and vacancies.)

Re:I thought the distinction was arbitrary already

[i kan reed]

Light absolutely has mass. For what definition of mass does a photon not have mass?

Re:I thought the distinction was arbitrary already

[Lord Crc]

The one scientists use today: invariant mass aka rest mass.

http://math.ucr.edu/home/baez/physics/ParticleAndNuclear/photon_mass.html

Re:I thought the distinction was arbitrary already

[ThreeKelvin]

Currently, the known massless particles are gauge bosons, the photon (carrier of electromagnetism) and the gluon (carrier of the strong force). Massless particle.

Re:I thought the distinction was arbitrary already

[i kan reed]

If you actually click the photon link in that article, it lists a mass.

I feel like I'm going to argue semantics forever if I push this though.

Re:I thought the distinction was arbitrary already

[Anonymous Coward]

The mass of a photon is related to its frequency by Planck's constant and E=mc^2.

So yes, photons have mass. (Specfically, m=hv/c^2).

They just don't have rest mass (because if they were at rest, their frequency would be zero).

Re:I thought the distinction was arbitrary already

[Anonymous Coward]

It's difficult to accept how many people dismissed your comment because they don't understand it. Maybe even more frustrating to me is how much the same folks want to be correct for their own benefit rather than the benefit of learning what may be true.

Re:I thought the distinction was arbitrary already

[Khashishi]

Matter has mass, but not all that has mass is matter. There are several types of polaritons, and some of them are clearly not matter, even though they have mass. Phonon-electromagnetic wave quanta are clearly not matter. Moreover, you state that light has no mass, which normally I wouldn't disagree with, but in the context of polaritons, what about light propagating through nonlinear media? I think it's totally appropriate to say it is massive.

Re:I thought the distinction was arbitrary already

[students]

The rest mass is the right mass to talk about in nearly all situations, rather than the relativistic mass.

Re:I thought the distinction was arbitrary already

[Khashishi]

The term mass, without additional qualifications, means rest mass. Unusual definitions of mass ought to be clearly labeled, such as relativistic mass.

Re:I thought the distinction was arbitrary already

[Anonymous Coward]

If you actually click the photon link in that article, it lists a mass.

You're right. It lists a theoretical mass of zero. And it has been experimentally verified to be less than a very small number, but no experiment will ever be able to show it is zero, because there's always some error.

I feel like I'm going to argue semantics forever if I push this though.

That's one way to avoid admitting you are wrong. Instead try a better article and actually learning something.

Re:I thought the distinction was arbitrary already

[Anonymous Coward]

It's difficult to accept how some anonymous cowards overlook peoples attempt to correct a misconception implied by a question like "For what definition of mass does a photon not have mass?"

Maybe even more frustrating to me is how much some anonymous cowards want to dismiss such attempts at correction rather than benefit from the potential teaching of what may be true.

Re:I thought the distinction was arbitrary already

[Anonymous Coward]

"A hole is a mobile positive charge with mass similar to the electron mass."

Actually, a hole is "the lack of an electron at a position where one could exist in an atom or atomic lattice." (See https://www.princeton.edu/~ach...)

A hole is like a bubble in a liquid. To say it has mass may help in the math, but it's a conceptual mass. A hole is in a very real sense a vacancy in the electron shell, left behind when an electron is excited away from the atom.

Re:I thought the distinction was arbitrary already

[iggymanz]

You are so busy being a pontificating numbnut you missed the sentence in the wikipedia article about relativistic mass

Re:I thought the distinction was arbitrary already

[Anonymous Coward]

Then you should go back to your Bachelor on fundamental particles. A hole is the lack of an electron, and has no mass. A photon at rest has a frequency of zero and so while you can claim it has no mass, that's because at rest it doesn't exist.

Re:I thought the distinction was arbitrary already

[Your.Master]

The question was:

Light absolutely has mass. For what definition of mass does a photon not have mass?

People have given very standard definitions for which a photon has no mass. Asked and answered.

The fact that relativistic mass is a thing is completely irrelevant to this discussion.

Re:I thought the distinction was arbitrary already

[Ceriel Nosforit]

More simply: light is massless but able to impart torque and momentum.

Convoluted literature like this seldom if ever mention a mechanism which makes this possible.

Re:I thought the distinction was arbitrary already

[Maritz]

Photons have zero rest mass.

Re:I thought the distinction was arbitrary already

[Maritz]

If a photon had rest mass, it would not travel at c (the speed of light). Neutrinos have a very small rest mass and travel close to c. If you research it, you'll find it is not semantics. These are technical terms with widely-accepted definitions.

Re:I thought the distinction was arbitrary already

[iggymanz]

Wrong, relativistic mass a very relevant point when talking of any "massless" particle that has real world consequences regarding momentum transfer, conservation of momentum etc. All "massless" particles must have relativistic mass, they cannot exist without it

Re:I thought the distinction was arbitrary already

[Bengie]

Matter has mass, but not all that has mass is matter

I'm not saying you're wrong, but I am having trouble finding a nice physics definition of "mass". All that I've found pretty much just says "mass is a property of matter".

Re:I thought the distinction was arbitrary already

[students]

Sure; this article is about exciton polaritons though.

You seem to be implying phonons are not matter. I would not call that "clear" at all. Maybe you should elaborate? Especially with respect to optical phonons.

Re:I thought the distinction was arbitrary already

[Khashishi]

Unfortunately, the term matter isn't universally agreed upon. Let's look at the definitions in wikipedia:
1. Does it have mass and volume (occupies space)? A phonon has mass, and maybe has volume, but doesn't 'occupy space' because it is a boson.
2. relativity, has rest mass? Phonons don't fit the equation E^2 = m^2 c^4 + p^2 c^2, because they have nonlinear dispersion equations, so it doesn't really make too much sense to talk about them at rest. They aren't Lorentz invariant, since they depend on the velocity of the material they are traveling through.
3. Is it made of atoms. Phonons are not made of atoms.
4. Is it made of electrons and baryons. no.
5. Is it made of quarks and leptons? No

Re:I thought the distinction was arbitrary already

[Khashishi]

There are two types of mass: inertial mass and gravitational mass. As far as we know, these two are equivalent.
Inertial mass is the resistance to motion (change in velocity). In Newtonian terms, F = ma. In special relativity, F = dp/dt = d(gamma*m*v)/dt
So, you can define mass as long as you can define a velocity and acceleration.

Gravitational mass is associated with gravity. In Newtonian physics, F = -G*m1*m2/r^2. In general relativity, gravitational mass is equivalent to rest energy. Gravity is given by Einstein's field equations which depend on the stress-energy tensor, which is a 4x4 matrix. The [0,0] element of the matrix is the rest energy density, which is the gravitational mass density/c^2.

Holodeck!!!!

[Anonymous Coward]

Holodeck anyone!!!!!

Re:Holodeck!!!!

[Anonymous Coward]

So depending on how long you've lived in a holodeck for, you will either walk out and *plop* into a pile of bio-goo, or you will disappear once all together once passed through the Arch. Point is, don't eat holo-food or drink holo-water.

Re:Holodeck!!!!

[wonkey_monkey]

*plop* into a pile of bio-goo

People should clean it out after they've used it.

Re: I thought the distinction was arbitrary alread

[i kan reed]

Let's see here:

I thought the distinctions made already are already mostly ones of convenience and scale:

Independent clause introducing the rest of the post

Matter is slow and heavy enough to mostly be possible to model as point masses

Independent clause describing matter's characteristics

, while

Comma and conjunction to join two independent clauses

light is fast, light, and numerous enough to be more convenient to treat as non-discrete energy than as individual photons.

Independent clause describing the properties of light.

Which part went so far over your head?

Cliche Machine

[Tablizer]

Sharknado.....with quantum lasers on their heads!

(Sharknado III should actually do that. Some military experiment using armed sharks goes awry in the Quantum Whirlpool tank, and flying, zapping sharks are everywhere. Sure it's silly, but so was Sharknado I.)

Re:Cliche Machine

[geekoid]

Nice geocities link.

Re:Cliche Machine

[Tablizer]

It actually worked a year ago. They didn't shut down paying accounts until recently.

Re: I thought the distinction was arbitrary alread

[just_another_sean]

Made perfect sense to me. The Overrated moderation on the other hand doesn't make much sense considering his comment wasn't even rated yet.

Ignorance does not equal a new state

[ourlovecanlastforeve]

Just because you can't discern the difference between light and matter in this state -- this does not mean they are the same thing.

Re:Ignorance does not equal a new state

[Anonymous Coward]

Actually, didn't the article perfectly describe a photon?
http://physics.about.com/od/lightoptics/f/photon.htm

Re:Ignorance does not equal a new state

[Anonymous Coward]

Just because you can't discern the difference between light and matter in this state -- this does not mean they are the same thing.

Both inherit from the Energy implementation, so depending at what level you are looking at them they are in fact the same thing.

Re:Ignorance does not equal a new state

[michelcolman]

Just because you can't discern the difference between light and matter in this state -- this does not mean they are the same thing.

Exactly, if you just move to a different state that has different laws, and maybe even a different definition of pi, you'll find that it's perfectly legal to discern between light and matter.

Re: I thought the distinction was arbitrary alread

[sexconker]

It's i kan reed.
Just skip over it.

Re: I thought the distinction was arbitrary alread

[ArcadeMan]

Have you seen his name?

Next up...

[prisoner-of-enigma]

Next up, Halo light bridges!

Re: I thought the distinction was arbitrary alread

[Anonymous Coward]

Why? You never do.

Re: I thought the distinction was arbitrary alread

[Artifakt]

Then the mod system was abused by somebody who either doesn't understand what simple English means or deliberately chose to misuse their tiny, trivial amount of power, probably because they have such a lack of a real life that they actually get an ego boost from it. Why are you sticking up for that?

Re: I thought the distinction was arbitrary alread

[sexconker]

U mad, i kan reed?

Re: I thought the distinction was arbitrary alread

[Anonymous Coward]

'Anonymous Coward' - October 2014:

Triple cases in 3 days. That's 9 cases by October 25. 27 by November 1. Over 2000 by the end of November. 170,000 by the end of the year. 14 million at the end of january and well over half the country by valentine's day.

U mad, sexconker? Keep trying, sexconker.

Re: I thought the distinction was arbitrary alread

[sexconker]

Nope, why would I be mad that you quoted your own dumbass post?

Re: I thought the distinction was arbitrary alread

[Anonymous Coward]

'Anonymous Coward' - October 2014:

Triple cases in 3 days. That's 9 cases by October 25. 27 by November 1. Over 2000 by the end of November. 170,000 by the end of the year. 14 million at the end of january and well over half the country by valentine's day.

'U' tell me, sexconker. Keep trying, sexconker.

Fire the Polariton Laser!

[Anonymous Coward]

Respect The Technobabble or the Jem'Hadar Will Shoot Plasmon-Polariton Beams At You!

Almost there.

[DiegoMartinez]

I'm glad it isn't named the Australian National University of Science.

Which way?

[Anonymous Coward]

Since it's Australia, did it spin turnwise or widdershins?

Re: I thought the distinction was arbitrary alread

[Maritz]

You certainly kan..!

IMHO this is important

[Anonymous Coward]

IMHO this is important for a different reason. We all know about the wave nature of matter and electron diffraction. So we surely all know that electrons and positrons are hybrid particles that have properties of both matter and light. The general idea goes back to Maxwell's "molecular vortices" and Thomson and Tait's "vortex atoms", which were ahead of their time. See On Vortex Particles by David St John for more on that. Peter Tait was the guy who came up with knot tables, and TQFT is related to knot theory. See the blue trefoil at http://en.wikipedia.org/wiki/Trefoil_knot , start at the bottom left and trace round anticlockwise calling out the crossing-over directions: up down up. Anyhow, the moot point is this: the electron is a Dirac bispinor. It's a quantum whirlpool too. To appreciate that, combine radial "electric field lines" with concentric "magnetic field lines" to depict the electron's electromagnetic field. See this picture:

http://bogpaper.wpengine.com/wp-content/uploads/2013/08/emfield.jpg

The electromagnetic field depiction on the right resembles the frame-dragging of the gravitomagnetic field. And IMHO it's intuitive: electrons and positrons don't literally throw photons back and forth. Positronium doesn't twinkle, nor do hydrogen atoms, and magnets don't shine. Instead electrons and positrons move linearly and rotationally rather like a cyclone and an anticyclone. But in 3D. See Adrian Rossiter's spindle-sphere torus animation for that. Think of it as the thing in the middle of the spiral, "the eye of the storm", as it were:

http://www.antiprism.com/album/misc/spindle_tor2_anim.gif

John Duffield