How 'spooky' quantum mechanical laws may affect everyday objects (Update)

Jul 01, 2010 by Holly Martin
An optical micrograph of one of the samples measured by the research team is shown here. The electrical contacts are at the top and bottom. The gold gates used to form the QPC tunnel barrier are also labeled. Credit: Joel Stettenheim, Dartmouth College

(PhysOrg.com) -- In a study published in the July 1 issue of the journal Nature, Dartmouth researchers describe one example of the microscopic quantum world influencing--even dominating, they say--the behavior of something in the macroscopic classical world.

"One major question in physics has to do with the connection between the microscopic and macroscopic worlds," said Alex Rimberg, associate professor of physics at Dartmouth College.

In the microscopic world, tiny sub-atomic particles such as photons and electrons, obey the sometimes bizarre laws of quantum mechanics. Meanwhile objects in the macroscopic world, generally anything visible with the naked eye, conform to the laws of classical physics discovered by Newton in the 17th century.

But a little more than 300 years after Newton, Einstein proved that light consists of tiny "packets" of energy, called quanta. This discovery marked the beginning of quantum theory, though it took decades of further work by several great scientific minds to finally settle on the modern theory of quantum mechanics.

One of the strangest laws of quantum mechanics is the Uncertainty Principle, first noted by German physicist and Nobel Laureate Werner Heisenberg in 1927. Heisenberg realized that when trying to locate a fast-moving particle, such as an electron, it was impossible to pin down both its position and its momentum at the same time.

"To do a measurement, an experiment has to interact with whatever is being measured," explained Rimberg. "But interaction means ultimately that you must exert a force on what you're measuring. If you're trying to measure the position of an object, any measurement will make the object move in an unpredictable and random way. This tendency to randomly affect what you are measuring is called "backaction."

Einstein could never accept this idea--that the act of measurement changes the object being measured--on philosophical grounds, and fought it until his dying breath. But the uncertainty principle is now known to be true for all quantum-level interactions.

What is not yet known is how the quantum and classical worlds relate. "What we don't understand, really, is how classical behavior emerges from as systems become larger and larger," Rimberg said. "We also don't really understand how large an influence quantum mechanics can have on the classical world we live in."

Making it real

Rimberg and colleague Miles Blencowe, both supported by grants from the National Science Foundation (NSF), have now led a team of researchers in demonstrating quantum mechanical events affecting the classical world.

The scientists didn't start out to accomplish any such thing, according to Rimberg. Instead, they were trying to measure fast changes in charge at nanometer scales.

To do this, they first created tiny semiconductor crystals, similar to a computer chip, each about 3 millimeters (about 1/10 of an inch) across. They deposited gold electrical gates running over the crystal, leaving a tiny break of only about a few hundred micrometers in the middle of the chip. This break is called a "quantum point contact," or QPC.

By hooking the chip up to an electrical circuit, electrons flow through metal contacts until they hit the QPC. And that's where they started to see one of quantum mechanics' quirks.

"You can think of the QPC as a tunnel barrier, sort of a wall for electrons," Rimberg explained. "When the wall is sufficiently high, the electrons do not have enough energy to go over it. If electrons were classical objects, that would be the end of the story. But since electrons obey the laws of quantum mechanics, instead of going over the barrier they can also "quantum tunnel" through it."

Thus, when a stream of electrons in an electrical current approaches the QPC, each electron in the stream randomly "chooses" to reflect backward off the barrier or go through it.

"This random process introduces noise into the electrical current, caused by random fluctuations in the number of electrons going through at any time," said Rimberg. "Because this noise is generated quantum mechanically, it is sometimes referred to as quantum noise."

Measuring quantum noise

For this experiment, the scientists used semiconductor crystals made of gallium arsenide, which happen to exhibit a property called piezoelectricity. The term "piezoelectric" means that an electrical current traveling through the crystal causes a mechanical or physical movement of the crystal itself, similar to the way a sponge expands when water hits it.

Piezoelectric are sometimes called resonators, because they can resonate, or vibrate, in reaction to electrical signals. These resonators can move in different ways-stretching or bending, depending on the frequency of the signal and the shape of the crystal.

"The three-dimensional vibration of a resonator crystal is exactly like the you get if you strike a tuning fork, or run a wet finger about the rim of a wine glass," Rimberg explained. "The glass (or tuning fork) starts to hum with a musical note; that's because there is a particular kind of vibrational pattern, determined by its geometry, that the atoms in the wine glass collectively take part in."

In the same way, the electrons bouncing off the QPC "wall" apply a random "backaction" force to the crystal, Rimberg said. In this case, the backaction force just happened to vibrate the crystal at one of its favorite frequencies. When the researchers measured the electrical current versus frequency and found strong peaks indicating that the backaction was creating a feedback loop, it took them by surprise.

"Neither I nor anyone else anticipated the spectral features that show the samples are vibrating," Rimberg said. "It took us quite a bit of time and effort to convince ourselves that it was a real effect, and yet more time and effort to figure out what it was."

Uncertainty in action

"In our case, the current running through the QPC gives information about the position of the semiconducting crystal that the QPC lives in," Blencowe said. "But because of the quantum noise in the current, at any given time there are random fluctuations in the number of electrons (on the order of 10,000 or so) on either side of the QPC."

And because these electrons have an electrical charge, they exert a piezoelectric force on the crystal, making it move. "The remarkable thing is that only 10,000 or so electrons are able to make all 1020 (100 quintillion) atoms in the crystal move at once," said Blencowe.

"The difference in size between the two parts of the system is really extreme," Blencowe explained. "To give a sense of perspective, imagine that the 10,000 electrons correspond to something small but macroscopic, like a flea. To complete the analogy, the crystal would have to be the size of Mt. Everest. If we imagine the flea jumping on Mt. Everest to make it move, then the resulting vibrations would be on the order of meters!"

"Our work is a direct example of the microscopic influencing, and even dominating the behavior of something in the macroscopic classical world," Rimberg said. "The motion of the semiconducting crystal is not dominated by something classical like thermal motion, but instead by the random in the number of tunneling electrons."

And in this case, Rimberg pointed out, the macroscopic world also influences the quantum world, because the crystal's vibrations cause the electrons to tunnel in large bunches.

In future research the team could take several possible directions. "First, we will actually use the QPC for charge detection, as we had intended to all along," Rimberg said. "Second, we'll continue to look at questions regarding the quantum-classical transition, but with resonators that are smaller than these crystals--things that are in the murky borderland between the much better understood quantum and classical regimes." This borderland is sometimes known as the "mesoscopic" scale.

"The study of these kinds of systems advances fundamental knowledge and also addresses some very practical questions, including: What are the fundamental limits of measurement? And what is the most sensitive measurement device that can be made?" said Daryl Hess, a program manager in NSF's Division of Materials Research.

"Questions of this kind become more pressing as our science and technology shrink to ever smaller scales with the vision of devices, electronic and mechanical, that are perhaps only a few atoms in one or more dimensions," added Hess. "At these scales, devices could show some aspects that appear squarely in the world of and others that appear to be squarely in the world of classical mechanics."

Explore further: The importance of three-way atom interactions in maintaining coherence

More information: Nature paper: www.nature.com/nature/journal/… ull/nature09123.html

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Jigga
1 / 5 (7) Jun 30, 2010
IMO we cannot estimate the fuzzy boundary between real and quantum or relativity worlds exactly, but we can find a boundary, where quantum and relativity phenomena compensate mutually.

As J.A.Wheeler derived by geon model in 1964, general relativity predicts, all massive objects should collapse inside of singularities soon or later. The quantum mechanics predicts exactly the opposite destiny for all material objects: it cannot incorporate the gravity, on the contrary: from Schrodinger equation follows, the wave packets of all free particles should expand and evaporate into infinity.

IMO these two theories are compensating mutually just at the distance/energy density scale of cosmic background noise of average wavelength in 1,9 cm range: all smaller objects will evaporate in this radiation, all larger objects will condense gradually into larger objects.

This distance range corresponds the size of human neurons too, so it may be actually observer dependent.
Caliban
2 / 5 (5) Jun 30, 2010
I've changed my mind, and decided that there is no missing mass, and there is no dark matter/dark energy.

The baryonic universe is just the solid/particulate/observable portion of a larger whole that is mainly constituted of a/the quantum energy portion.

The zero point energy/quantum fluctuation/vacuum energy are the boundary -or phase transition zone- between the two.

Did I just solve the problem?
Jigga
1 / 5 (4) Jun 30, 2010
Did I just solve the problem?
I can imagine, the total volume of space compacted inside of matter is roughly equal the volume of cosmic space. If the quantum fluctuations are cosmic microwave noise, then the boundary between intrinsic and extrinsic perspective corresponds your dividing scheme.

But to explain dark matter or dark energy phenomena in such a way is not so trivial. I don't see any direct connection of this symmetry to "missing mass" or "dark matter/energy" problem here.

Do you?
NeuroPulse
5 / 5 (6) Jun 30, 2010
I do not think there is a division between the quantum world and classical world. It is a continuum, and it is *all* quantum world. On the macroscopic scale, we just do not notice it. We have been able to put increasingly larger objects in superposition. It is a matter of isolating them and preventing them from interacting with anything which collapses the superposition. *If* you could completely isolate a baseball, it would behave like particles in the double slit experiment. But macroscopic objects instantly interact with something else and the superposition is immediately collapsed.
Ashibayai
Jun 30, 2010
This comment has been removed by a moderator.
Jarek
1 / 5 (1) Jul 01, 2010
'Quantum' is about unitary/wavelike evolution - the same we have on water surface or in field theories we are using on all scales (GRT, EM, Klein-Gordon, QFT): if after linearization we write Euler-Lagrange evolution equations in eigenbase of the differential operator, we can look at it as superposition of rotations of coordinates ('waves').
We cannot fully trace its evolution - in such cases we use thermodynamics: assume some maximizing entropy statistical ensemble among possible situations, like while describing gas using a few parameters instead of tracing all particles.
In physics with particles - localized solutions (solitons?), if instead of maximizing entropy locally what leads to Brownian motion in continuous limit, we do it right - globally - we get going to squares of coordinates of dominant eigenvector of (discrete) Hamiltonian probability density - that when we cannot trace unitary evolution, we should assume wavefunction collapse ( http://arxiv.org/pdf/0910.2724 )
KBK
1.7 / 5 (6) Jul 01, 2010
"Einstein could never accept this idea--that the act of measurement changes the object being measured--on philosophical grounds, and fought it until his dying breath."

MAJOR FAIL.

Einnie did not do so. In 1928, he introduced his Unified Field Theory in Russia, at a conference. It is extant and it ~IS~ FULLY engineerable. It is partially based on the works of 1921 Nobel Winner Walter Gerlach.

BOTH men went dead silent, after the war. Both knew that their mechanically based equivalency and engineerable theories where HUGELY dangerous for man.

Gerlach never worked in those fields again - after working at the deepest level of the Nazi machine, at a security level above that of the bomb projects (anti-gravity, aetheric energies, etc).

Einstein went silent (deny, deny, deny!) as he knew the danger of a commonly engineerable fabric of space/time would tear the then animalistic (and still irresponsible and violent) man to pieces.

Everything went black ops, and underground -literally.
ubavontuba
3 / 5 (2) Jul 01, 2010
I've changed my mind, and decided that there is no missing mass, and there is no dark matter/dark energy.

The baryonic universe is just the solid/particulate/observable portion of a larger whole that is mainly constituted of a/the quantum energy portion.

The zero point energy/quantum fluctuation/vacuum energy are the boundary -or phase transition zone- between the two.

Did I just solve the problem?
LOL. Perhaps you have!

KBK
2 / 5 (4) Jul 01, 2010
Your first clue that I'm not kidding:

"The phenomenon is known as space quantization, and it could be predicted theoretically that silver atoms could have only two orientations in an external field. To test this, Stern with Walter Gerlach passed a beam of silver atoms through a nonuniform magnetic field and observed that it split into two separate beams. This, the famous Stern–Gerlach experiment, was a striking piece of evidence for the validity of the quantum theory and Stern received the 1943 Nobel Prize for physics for this work."

~~~~~~~~~~~~~~~~~~~~
So Gerlach was working on these bits of information as far back as 1920. As an example, the experiment and the results were still easily within the framework of mechanistic considerations, no quantum theory required.

Thus, resonance (F=ma) and angular aspects could be utilized to manipulate space/time, in theory, in 1920.

Here is a proof on that, right here, on physorg:

http://www.physor...740.html
KBK
1 / 5 (2) Jul 01, 2010
I do not think there is a division between the quantum world and classical world. It is a continuum, and it is *all* quantum world. On the macroscopic scale, we just do not notice it. We have been able to put increasingly larger objects in superposition. It is a matter of isolating them and preventing them from interacting with anything which collapses the superposition. *If* you could completely isolate a baseball, it would behave like particles in the double slit experiment. But macroscopic objects instantly interact with something else and the superposition is immediately collapsed.


Close, it is averaged out. due to the mass (large intertwined number) if individual wave/particle interactives.

Thus the whole probability aspect of multiple dimensions that are constantly splitting in front of us, in this 'linear/unidirectional time' universe or dimensional reference we currently use as our basis of understanding.
KBK
1 / 5 (5) Jul 01, 2010
Most people here are cursed by the lack of right brain thinking, and dominated by left brain linear thinking. This leads to their inability to achieve a balance that allows them to see the forest and the trees at the same time.

The problem has never been one of logic or understandings, it is in the underpinnings of the psychology that is within the base emotions, ie the hindbrain.

It is in the communication system that brings the two hemispheres together. The problem gets down to the connectivity on the base components of the mind, not the so-called 'higher logic' centers.

Left brain scientific types who are dominated by their left brain have internal communication issues on the level of 'wiring'. They need some crainial balance and to learn to use the other 50% of their brain mass. This can be frightening to those types, so it is NEVER considered.

This fear is the hindbrain itself working hard to maintain it's control over the formation of logic, so they miss the point entirely.
Ozz
Jul 01, 2010
This comment has been removed by a moderator.
Glyndwr
5 / 5 (4) Jul 01, 2010


Einstein went silent (deny, deny, deny!) as he knew the danger of a commonly engineerable fabric of space/time would tear the then animalistic (and still irresponsible and violent) man to pieces.



Well it was einstein who said the universe and human's stupidity are infinite and I am not so sure about the former..........so I can understadn if he went quiet.....but what are these underground truths of engineerable fabrics you state?

mattytheory
5 / 5 (3) Jul 01, 2010

VestaR - 12 hours ago:
and it is *all* quantum world

From certain remote perspective yes, but quantum mechanics and general relativity differ in many orders by their predictions.


You are assuming that our understandings of these two seemingly separate yet related descriptions of the universe are complete. I would argue that Relativity and QM as we understand them today are incomplete and that NeuroPulse's comments (a philosophical application of a GUT) will turn out to be correct. It is all a continuum and like everything else context is key... or in this case: scale.
Jigga
1 / 5 (4) Jul 01, 2010
When some equation says A = 1 and the equation of some other theory says A = 2, then there is no possibility, how to reconcile both theories in formally rigorous way, because atemporal math is based on the assumption, 1 never ever equals 2.

Of course, we can construct some other theory, which will use only consistent subset of postulates of both theories (if any) - but there's no hope for formal reconciliation of quantum mechanics and relativity in their original forms at the moment, when they differ in their predictions already.
cmn
5 / 5 (3) Jul 01, 2010
Curious, the resonance of this crystal caused an increase in electron tunneling... In this state, isn't the crystal also a probabilistic object, both "particle" and wave, as it's macroscopic location is constantly in motion. Wouldn't the QPC also become probabilistic, allowing for more of an "opportunity" for the electrons to tunnel over (or through) this wall?
Hesperos
5 / 5 (2) Jul 03, 2010
1 never ever equals 2.

Are you sure? :-)
Jigga
3 / 5 (2) Jul 03, 2010
1 never ever equals 2.
In formal math, yes. In real world it's quite common.
frajo
3 / 5 (4) Jul 03, 2010
1 never ever equals 2.
In formal math, yes.

You seem to prefer unspoken assumptions to clear definitions. Unfortunately, formal math is quite demanding - it wants you to define each symbol you use, even the symbols "1", "2", and "=". Otherwise, formal math won't ever fall in love with you.
Hunnter
1 / 5 (2) Jul 04, 2010
and it is *all* quantum world

From certain remote perspective yes, but quantum mechanics and general relativity differ in many orders by their predictions.

But that is down to the fact that GR is nowhere near complete. GR is a pretty broken model, at best, when it is expanded in scope to the whole universe.
QM is more correct, with a lot of actual experimental evidence behind it.
There are some headaches still to be ironed out, but it will be the one ironed out, GR is just a mess of ideas and some experimentation that came many years after some equations. It only works with a very defined scope. Eventually, GR will be integrated with QM, but most of what it made it what it is will be fixed and won't resemble what we know it as now.
ShawnQuest
not rated yet Jul 06, 2010
Maybe I am missing the point, but this seems to be acting like a mini-capacitor.
Skeptic_Heretic
not rated yet Jul 06, 2010
GR is just a mess of ideas and some experimentation that came many years after some equations. It only works with a very defined scope. Eventually, GR will be integrated with QM, but most of what it made it what it is will be fixed and won't resemble what we know it as now.
QM is a more correct version of GR, the issue is QM cannot directly address gravity, where as GR attempts to do so through scale of interaction.

We know that GR isn't all that can be said as it has no explanitive power over the anomalous observations we have in how singularities orbit one another amongst other things, while QM at least begins to hint at what drives these forms of interaction.

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