Revealing quantum flow

Dec 28, 2012
Wigner flow’s stagnation points’ positions across phase space as a function of time. Credit: University of Hertfordshire

(Phys.org)—UK-based physicist Ole Steuernagel from the University of Hertfordshire, alongside Dimitris Kakofengitis and Georg Ritter, have found that a new powerful tool they call 'Wigner flow' is the quantum analogue of phase space flow.

Wigner flow provides information for similar to that gleaned from phase space trajectories in . Wigner flow can be used for the visualisation of quantum dynamics. Additionally, and perhaps even more importantly, Wigner flow helps with the abstract analysis of quantum dynamics using topological methods.

Ole Steuernagel, from the University's Science and Technology Research Institute, said: "Because trajectories are missing in quantum phase space, physicists did not pay much attention to the associated flow-fields, although these do exist. Now, our research shows that quantum phase space flow is well worth studying."

In classical physics, phase space trajectories give rise to flow-fields representing the dynamics of the system along its trajectories; they yield additional insight into a system's behaviour.

phase space trajectories do not exist because Heisenberg's does not allow for the formation of sharply defined trajectories. But have not given up entirely on phase space. The study of the next best thing, the movement of ' phase space-based probability distributions has actually boomed in recent years.

Sophisticated schemes for the reconstruction of the most prominent of these distributions, 'Wigner's function', from experimental data, have set quantum phase space analysis on a firm footing. Yet, since quantum trajectory studies cannot be carried out, some of the power of established classical methods is missing.

The researchers have been studying Wigner flow, which is based on the dynamics of Wigner's function, and have shown that it reveals new and surprising features of space dynamics. It forms, for example, vortices that spin the 'wrong' way round and which appear in the 'wrong' part of phase space, when viewed from a classical physics standpoint. So, such dynamical patterns are manifestations of the quantum nature of the system.

On top of such new riches the team has established the existence of a conservation law that reveals a new type of topological order for quantum dynamics. As an application they have shown that Wigner flow sheds new light on quantum tunnelling, the fundamental process that governs the workings of electronic computer circuits, and also the decay of radio-nuclides.

Explore further: Mapping the optimal route between two quantum states

More information: The paper "Wigner flow reveals topological order in quantum phase space dynamics" is published in Physical Review Letters.

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User comments : 10

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ValeriaT
1 / 5 (5) Dec 28, 2012
A well known example of the Wigner flow is the motion of magnetic domains, which is followed with Barkhausen noise.
Sean_W
1.7 / 5 (6) Dec 28, 2012
Soooooo... How's the weather?
Torbjorn_Larsson_OM
5 / 5 (4) Dec 28, 2012
Nice!

@ Valeria: "A well known example". Right... the article linked on that page is where the figs and the examples of the text is from, is their first detail study ("Wigner
flow has so far not been studied in detail") and is dated Aug 2012.

This is pretty much the press release of a published version. I think there has to be some societal response to these methods, and their examples, among scientists before they are ascertained to be "well known" respectively "(valid) examples".
vacuum-mechanics
1 / 5 (7) Dec 28, 2012
But quantum physicists have not given up entirely on phase space. The study of the next best thing, the movement of quantum physics' phase space-based probability distributions has actually boomed in recent years.
It is interesting to note that even we know that we cannot measure the momentum and position with a greater accuracy of the uncertainty principle, but the problem is that why it is so, or what is its mechanism? Maybe this physical view could help us to understand it.
http://www.vacuum...19〈=en
ValeriaT
2 / 5 (4) Dec 28, 2012
there has to be some societal response to these methods
Phase space flow is here about some time already. It's sometimes called the Wigner-Liouville flow. It has its topic at Wikipedia - so I presume, it's well recognized approach between specialists.
Sean_W
1.7 / 5 (6) Dec 30, 2012
Soooooo... How's the weather?


No seriously. Did the author of this article even consider defining even one of his terms for a non-PhD audience? The piece spoke of a "system's behaviour" without even giving an indication of what sort of system they are speaking of. Don't they have news groups for physicists and mathematicians to discuss their work where everyone has their educational background? This is analogous to a network using a prime time national news show to have pundits discus circuit diagrams--and not even telling the audience what the device they are discussing is for.
srikkanth_kn
2.5 / 5 (6) Dec 31, 2012
Soooooo... How's the weather?


No seriously. Did the author of this article even consider defining even one of his terms for a non-PhD audience? The piece spoke of a "system's behaviour" without even giving an indication of what sort of system they are speaking of. Don't they have news groups for physicists and mathematicians to discuss their work where everyone has their educational background? This is analogous to a network using a prime time national news show to have pundits discus circuit diagrams--and not even telling the audience what the device they are discussing is for.


Agreed... no heads, no tails, too short for any meaningful understanding
antialias_physorg
3.7 / 5 (3) Dec 31, 2012
Did the author of this article even consider defining even one of his terms for a non-PhD audience?

Why should he? His paper is written for a grad student/PhD audience. It's not his job to put this in laymen's terms (which can't be done without generating major misunderstandings on the part of the laymen because they are missing the fundamentals of quantum mechanics)

It's the job of those WANTING to understand such a paper to go out and educate themselves to the point where they can (which isn't too hard in this case - just look up Wiegners function and phase space).

Science isn't like school where you just wait until a teacher feeds it to you with a spoon (and science journalism is certainly not such a teacher). Science is hard work - that you have to do yourself.
Ophelia
1 / 5 (1) Jan 02, 2013
Did the author of this article even consider defining even one of his terms for a non-PhD audience?

Why should he? His paper is written for a grad student/PhD audience. It's not his job to put this in laymen's terms.


I guess I missed the part in school where the instructor told me I had to do research before I picked up a generally published article and read it rather than the actual paper. Just another day of nodding off.

Now I know why I never understand anything I read about economics, biology, medicine, philosophy, mathematics, chemistry, history, politics, agriculture, agronomy, herbology, wicca .......

Just didn't do the research first.
antialias_physorg
not rated yet Jan 02, 2013
Just didn't do the research first.

That's just how it goes beyond a certain level. Science isn't kindergarten anymore.
At some point you have to take responsibility for your own education.

Most of all at the forefront of science there really isn't anyone who can tell you about this stuff, because it's brand new. So you have to just try and get to grips with it as best you can.

Some enjoy this activity - and those expand their horizon.
Others feel cheated because they somehow feel they should be entitled being handing the solution - and those get stuck at the level they're at.

Remember: The number of people who understand an new paper fully is intially one (the one writing it). And I really don't see why you would expect researchers to also be fabulous teachers (or interested in making people who will never use their work knowledegeable about it). Research is their job. They have enough on their plate doing that.