Measuring the smallest magnets: Physicists measured magnetic interactions between single electrons

Jul 28, 2014
This is an illustration showing the magnetic field lines of two electrons, arranged so that their spins point in opposite directions. Credit: Dr. Roee Ozeri, Weizmann Institute of Science

Imagine trying to measure a tennis ball that bounces wildly, every time to a distance a million times its own size. The bouncing obviously creates enormous "background noise" that interferes with the measurement. But if you attach the ball directly to a measuring device, so they bounce together, you can eliminate the noise problem.

As reported recently in Nature, physicists at the Weizmann Institute of Science used a similar trick to measure the interaction between the smallest possible magnets – two single electrons – after neutralizing magnetic noise that was a million times stronger than the signal they needed to detect.

Dr. Roee Ozeri of the Institute's Physics of Complex Systems Department says: "The electron has spin, a form of orientation involving two opposing magnetic poles. In fact, it's a tiny bar magnet." The question is whether pairs of electrons act like regular bar magnets in which the opposite poles attract one another.

Dr. Shlomi Kotler performed the study while a graduate student under Dr. Ozeri's guidance, with Drs. Nitzan Akerman, Nir Navon and Yinnon Glickman. Detecting the magnetic interaction of two electrons poses an enormous challenge: When the electrons are at a close range – as they normally are in an atomic orbit – forces other than the magnetic one prevail. On the other hand, if the electrons are pulled apart, the magnetic force becomes dominant, but so weak in absolute terms that it's easily drowned out by ambient magnetic noise emanating from power lines, lab equipment and the earth's .

The scientists overcame the problem by borrowing a trick from quantum computing that protects quantum information from outside interference. This technique binds two electrons together so that their spins point in opposite directions. Thus, like the bouncing tennis ball attached to the measuring device, the combination of equal but opposite spins makes the electron pair impervious to magnetic noise.

The Weizmann scientists built an electric trap in which two electrons are bound to two strontium ions that are cooled close to absolute zero and separated by 2 micrometers (millionths of a meter). At this distance, which is astronomic by the standards of the quantum world, the magnetic interaction is very weak. But because the electron pairs were not affected by external magnetic noise, the interactions between them could be measured with great precision. The measurement lasted for 15 seconds – tens of thousands of times longer than the milliseconds during which scientists have until now been able to preserve quantum data.

The measurements showed that the interacted magnetically just as two large magnets do: Their north poles repelled one another, rotating on their axes until their unlike poles drew near. This is in line with the predictions of the Standard Model, the currently accepted theory of matter. Also as predicted, the magnetic interaction weakened as a function of the distance between them to the power of three.

In addition to revealing a fundamental principle of particle physics, the measurement approach may prove useful in such areas as the development of atomic clocks or the study of quantum systems in a noisy environment.

Explore further: Exploring the magnetism of a single atom

More information: Nature 510, 376–380 (19 June 2014) DOI: 10.1038/nature13403

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User comments : 15

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George_Rajna
Jul 28, 2014
This comment has been removed by a moderator.
Whydening Gyre
5 / 5 (6) Jul 28, 2014
Geez, George - what CAN'T you explain with that link?
Uncle Ira
3.7 / 5 (6) Jul 28, 2014
Geez, George - what CAN'T you explain with that link?


I never clicked on him, but he must be a good one. Ol George-Skippy sure is proud with him huh?
Whydening Gyre
5 / 5 (3) Jul 28, 2014
I STILL wanna know what school(s) Academia.edu is affiated with...
Uncle Ira
3.7 / 5 (6) Jul 28, 2014
I STILL wanna know what school(s) Academia.edu is affiated with...


The International Academies of Crankpots as best I can tell. I think that interweb place will let anybody start a thing for pretending to be the Scientist-Skippy.
Whydening Gyre
5 / 5 (6) Jul 28, 2014
K... Looked it up on Wiki.
http://en.wikiped...emia.edu
Not discounting any potential legitimacy, but -
Pay special attention to the Domain Name blurb...
Uncle Ira
3.4 / 5 (5) Jul 28, 2014
K... Looked it up on Wiki.
http://en.wikiped...emia.edu
Not discounting any potential legitimacy, but -
Pay special attention to the Domain Name blurb...


Well according to that it seems be about like the physorg commentators here. Anybody can postup anything they want to call a theory. But the postums look more scientifical than the commentators here where you can only use 1000 letters and only regular letters for your theories.
TechnoCreed
4.2 / 5 (5) Jul 28, 2014
K... Looked it up on Wiki.
http://en.wikiped...emia.edu
Not discounting any potential legitimacy, but -
Pay special attention to the Domain Name blurb...
Good catch on that one. Thank you WG
Dr_toad
Jul 28, 2014
This comment has been removed by a moderator.
arom
1.7 / 5 (6) Jul 28, 2014
Dr. Roee Ozeri of the Institute's Physics of Complex Systems Department says: "The electron has spin, a form of orientation involving two opposing magnetic poles. In fact, it's a tiny bar magnet." The question is whether pairs of electrons act like regular bar magnets in which the opposite poles attract one another….
The measurements showed that the electrons interacted magnetically just as two large magnets do: Their north poles repelled one another, rotating on their axes until their unlike poles drew near. This is in line with the predictions of the Standard Model, the currently accepted theory of matter….

This seems to be a good experiment which shows how the micro world look like; unfortunately the Standard Model, the theory of matter, have no explanation how and why the electrons act in this way. Maybe this idea could help to visualize how it works ….
http://www.vacuum...21〈=en
supamark23
4.4 / 5 (7) Jul 28, 2014
Hey arom, you're 100% wrong.
Whydening Gyre
5 / 5 (2) Jul 29, 2014
Hey arom, you're 100% wrong.

I mostly agree with that statement, Supa.
Now. Can you tell him WHY he's wrong (in a thousand characters or less)?
DeliriousNeuron
1 / 5 (3) Aug 02, 2014
Aunt ira....its about conveying information. Its all about ideas, different views and angles.
Auntie, there IS more to be discovered. Its not all about what you think is right/wrong.
If you'd actually contribute some pertinent information on here instead of bashing posters ideas, physorg would be better for us all.
Now Auntie, have u been reading all the new exciting papers on your favorite subject.
The Electric Universe Theory! :)
Captain Stumpy
4 / 5 (4) Aug 02, 2014
Its all about ideas, different views and angles
@delerious
IMHO - he isn't saying that it isnt...
Here is the problem with the site
you DON'T NEED to be an actual academic to be on the site
you DON'T NEED to be a legitimate scientist or even have a high school diploma to post your research OR COMMENT on the research of others (I just tested this by submitting a profile). so there is no real peer review... just a reddit (or PO) style comment section where you can bash the poster or praise them. Which makes as much sense as just posting original research to reddit or here
it is NOT accredited, nor affiliated with ANY institution of higher learning. it is basically a reddit for glory hound crackpots or a possible new way to distribute research

there is a REASON for peer review process! to keep PSEUDOSCIENCE (like EU) out of legitimate scientific papers and add SOME respectability to a submission
So far it (peer review) has been effective & worth it with RARE retractions etc
Uncle Ira
4 / 5 (4) Aug 02, 2014
Now Auntie, have u been reading all the new exciting papers on your favorite subject.
The Electric Universe Theory! :)


Nope, not too much. I mean I don't have time to read everything so I start with the good stuff first. Maybe in 10 or 9 years I will be able to get down to the crankpot stuffs.

So far you and the cantdrive-Nazi-Skippy have done a good job making sure that I feel good by putting it at the bottom of the to read next piles.
DeliriousNeuron
1 / 5 (1) Aug 02, 2014
Now Auntie, have u been reading all the new exciting papers on your favorite subject.
The Electric Universe Theory! :)


Nope, not too much. I mean I don't have time to read everything so I start with the good stuff first. Maybe in 10 or 9 years I will be able to get down to the crankpot stuffs.

So far you and the cantdrive-Nazi-Skippy have done a good job making sure that I feel good by putting it at the bottom of the to read next piles.

It will be much sooner than 10 years Ira. Don't be afraid of the unknown.
Uncle Ira
5 / 5 (1) Aug 02, 2014
It will be much sooner than 10 years Ira.


You think I can finish everything I want to read in less than 10 or 9 years? Every time I finish the one thing I usually get two more to add on the list. Like I said before, you and the cantdrive-Nazi-Skippy haven't made that electrical magnet universe stuff sound very interesting. So maybe I will check it out when I don't some interesting stuff laying around that I would rather read. But I will probably not have time to get to crankpot stuffs for awhile unless you make him more interesting.

Don't be afraid of the unknown.


That is a silly weird thing to say. Does it mean anything or was it just for filling out the postum's extra spaces? I can't remember the last time I was afraid of something. What you think I am afraid of? Not being interested in something doesn't mean being afraid something, I mean it doesn't down here, maybe it does up there where you are.

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