Science & Technology

New Research Suggests Electron Wave Function Can Be Split and Trapped

A canister of liquid helium contained in the blue cylinder allowed researchers to experiment with tiny electron bubbles solely 3.6 nanometers in diameter. The work means that the wave perform of an electron will be cut up and components of it trapped in smaller bubbles. Photograph: Mike Cohea/Brown College

A newly revealed examine from Brown College means that the quantum state of an electron — the electron’s wave perform — will be shattered into items and trapped.

Windfall, Rhode Island (Brown College) — New analysis by physicists from Brown College places the profound strangeness of quantum mechanics in a nutshell — or, extra precisely, in a helium bubble.

Experiments led by Humphrey Maris, professor of physics at Brown, recommend that the quantum state of an electron — the electron’s wave perform — will be shattered into items and these items will be trapped in tiny bubbles of liquid helium. To be clear, the researchers will not be saying that the electron will be damaged aside. Electrons are elementary particles, indivisible and unbreakable. However what the researchers are saying is in some methods more strange.

In quantum mechanics, particles don’t have a definite place in house. As an alternative, they exist as a wave perform, a chance distribution that features all of the doable areas the place a particle may be discovered. Maris and his colleagues are suggesting that components of that distribution will be separated and cordoned off from one another.

“We’re trapping the prospect of discovering the electron, not items of the electron,” Maris mentioned. “It’s just a little like a lottery. When lottery tickets are bought, everybody who buys a ticket will get a chunk of paper. So all these persons are holding an opportunity and you possibly can take into account that the possibilities are unfold all over. However there is just one prize — one electron — and the place that prize will go is set later.”

If Maris’s interpretation of his experimental findings is right, it raises profound questions in regards to the measurement course of in quantum mechanics. Within the conventional formulation of quantum mechanics, when a particle is measured — which means it’s discovered to be in a single explicit location — the wave perform is claimed to break down.

“The experiments we now have carried out point out that the mere interplay of an electron with some bigger bodily system, corresponding to a shower of liquid helium, doesn’t represent a measurement,” Maris mentioned. “The query then is: What does?”

And the truth that the wave perform will be cut up into two or extra bubbles is unusual as nicely. If a detector finds the electron in a single bubble, what occurs to the opposite bubble?

“It actually raises all types of fascinating questions,” Maris mentioned.

The new research is published in the Journal of Low Temperature Physics.

Electron bubbles

Scientists have puzzled for years in regards to the unusual habits of electrons in liquid helium cooled to close absolute zero. When an electron enters the liquid, it repels surrounding helium atoms, forming a bubble within the liquid about 3.6 nanometers throughout. The scale of the bubble is set by the strain of the electron pushing in opposition to the floor pressure of the helium. The strangeness, nevertheless, arises in experiments relationship again to the Nineteen Sixties how the bubbles transfer.

Within the experiments, a pulse of electrons enters the highest of a helium-filled tube, and a detector registers the electrical cost delivered when electron bubbles attain the underside of the tube. As a result of the bubbles have a well-defined measurement, they need to all expertise the identical quantity of drag as they transfer, and ought to subsequently arrive on the detector on the similar time. However that’s not what occurs. Experiments have detected unidentified objects that attain the detector earlier than the traditional electron bubbles. Through the years, scientists have cataloged 14 distinct objects of various sizes, all of which appear to maneuver sooner than an electron bubble could be anticipated to maneuver.

“They’ve been a thriller ever since they have been first detected,” Maris mentioned. “No person has a very good clarification.”

A number of prospects have been proposed. The unknown objects could possibly be impurities within the helium—charged particles knocked free from the partitions of the container. One other chance is that the objects could possibly be helium ions — helium atoms which have picked up a number of additional electrons, which produce a adverse cost on the detector.

However Maris and his colleagues, together with Nobel laureate and Brown physicist Leon Cooper, imagine a brand new set of experiments places these explanations to relaxation.

New experiments

The researchers carried out a collection of electron bubble mobility experiments with a lot better sensitivity than earlier efforts. They have been in a position to detect all 14 of the objects from earlier work, plus 4 extra objects that appeared steadily over the course of the experiments. However along with these 18 objects that confirmed up steadily, the examine revealed numerous extra objects that appeared extra hardly ever.

In impact, Maris says, it seems there aren’t simply 18 objects, however an successfully infinite variety of them, with a “steady distribution of sizes” as much as the scale of the traditional electron bubble.

“That places a dagger in the concept that these are impurities or helium ions,” Maris mentioned. “It will be exhausting to think about that there could be that many impurities, or that many beforehand unknown helium ions.”

The one approach the researchers can consider to elucidate the outcomes is thru “fission” of the wave perform. In sure conditions, the researchers surmise, electron wave capabilities break aside upon coming into the liquid, and items of the wave perform are caught in separate bubbles. As a result of the bubbles include lower than the total wave perform, they’re smaller than regular electron bubbles and subsequently transfer sooner.

Of their new paper, Maris and his group lay out a mechanism by which fission might occur that’s supported by quantum concept and is in good settlement with the experimental outcomes. The mechanism includes an idea in quantum mechanics referred to as reflection above the barrier.

Within the case of electrons and helium, it really works like this: When an electron hits the floor of the liquid helium, there’s some probability that it’s going to cross into the liquid, and some probability that it’s going to bounce off and carom away. In quantum mechanics, these prospects are expressed as a part of the wave perform crossing the barrier, and a part of it being mirrored. Maybe the small electron bubbles are shaped by the portion of the wave perform that goes via the floor. The scale of the bubble will depend on how a lot wave perform goes via, which might clarify the continual distribution of small electron bubble sizes detected within the experiments.

The concept that a part of the wave perform is mirrored at a barrier is commonplace quantum mechanics, Cooper mentioned. “I don’t assume anybody would argue with that,” he mentioned. “The non-standard half is that the piece of the wave perform that goes via can have a bodily impact by influencing the scale of the bubble. That’s what is radically new right here.”

Additional, the researchers suggest what occurs after the wave perform enters the liquid. It’s a bit like placing a droplet of oil in a puddle of water. “Someday your drop of oil types one bubble,” Maris mentioned, “Typically it types two, typically 100.”

There are parts inside quantum concept that recommend a bent for the wave perform to interrupt up into particular sizes. By Maris’s calculations, the particular sizes one may anticipate to see correspond roughly to the 18 steadily occurring electron bubble sizes.

“We expect this gives the perfect clarification for what we see within the experiments,” Maris mentioned. We’ve received this physique of knowledge that goes again 40 years. The experiments will not be improper; they’ve been executed by a number of individuals. Now we have a practice known as Occam’s razor, the place we attempt to provide you with the best clarification. This, as far as we are able to inform, is it.”

However it does increase some fascinating questions that sit on the border of science and philosophy. For instance, it’s essential to assume that the helium doesn’t make a measurement of the particular place of the electron. If it did, any bubble discovered to not include the electron would, in concept, merely disappear. And that, Maris says, factors to one of many deepest mysteries of quantum concept.

“Nobody is bound what really constitutes a measurement. Maybe physicists can agree that somebody with a Ph.D. carrying a white coat sitting within the lab of a well-known college could make measurements. However what about any individual who actually isn’t certain what they’re doing? Is consciousness required? We don’t actually know.”

Authors on the paper along with Maris have been former Brown postdoctoral researcher Wanchun Wei, graduate scholar Zhuolin Xie, and George Seidel, professor emeritus of physics.

Publication: W. Wei, et al., “Research of Unique Ions in Superfluid Helium and the Doable Fission of the Electron Wave Function,” Journal of Low Temperature Physics, 2014; DOI:10.1007/s10909-014-1224-3

Picture: Mike Cohea/Brown College

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