Scientists supersize quantum mechanics
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By Geoff Brumfiel
A team of scientists has succeeded in putting an object large enough to be visible to the naked eye into a mixed quantum state of moving and not moving.
Andrew Cleland at the University of California, Santa Barbara, and his team cooled a tiny metal paddle until it reached its quantum mechanical "ground state"-- the lowest-energy state permitted by quantum mechanics. They then used the weird rules of quantum mechanics to simultaneously set the paddle moving while leaving it standing still. The experiment shows that the principles of quantum mechanics can apply to everyday objects as well as as atomic-scale particles.
The work is simultaneously being published online today in Nature and presented today at the American Physical Society's meeting in Portland, Oregon.
According to quantum theory, particles act as waves rather than point masses on very small scales. This has dozens of bizarre consequences: it is impossible to know a particle's exact position and velocity through space, yet it is possible for the same particle to be doing two contradictory things simultaneously. Through a phenomenon known as "superposition" a particle can be moving and stationary at the same time--at least until an outside force acts on it. Then it instantly chooses one of the two contradictory positions.
But although the rules of quantum mechanics seem to apply at small scales, nobody has seen evidence of them on a large scale, where outside influences can more easily destroy fragile quantum states. "No one has shown to date that if you take a big object, with trillions of atoms in it, that quantum mechanics applies to its motion," Cleland says.
There is no obvious reason why the rules of quantum mechanics shouldn't apply to large objects. Erwin Schrödinger, one of the fathers of quantum mechanics, was so disturbed by the possibility of quantum weirdness on the large scale that he proposed his famous "Schrödinger's cat" thought experiment. A cat is placed in a box with a vial of cyanide and a radioactive source. If the source decays, it triggers a device that will break the vial, killing the cat. During the time the box is shut, Schrödinger argued, the cat is in a superposition of alive and dead--an absurdity as far as he was concerned.
Wonderful weirdness
Cleland and his team took a more direct measure of quantum weirdness at the large scale. They began with a a tiny mechanical paddle, or "quantum drum," around 30 micrometers long that vibrates when set in motion at a particular range of frequencies. Next they connected the paddle to a superconducting electrical circuit that obeyed the laws of quantum mechanics. They then cooled the system down to temperatures below one-tenth of a kelvin.
At this temperature, the paddle slipped into its quantum mechanical ground state. Using the quantum circuit, Cleland and his team verified that the paddle had no vibrational energy whatsoever. They then used the circuit to give the paddle a push and saw it wiggle at a very specific energy.
Next, the researchers put the quantum circuit into a superposition of "push" and "don't push," and connected it to the paddle. Through a series of careful measurements, they were able to show that the paddle was both vibrating and not vibrating simultaneously.
"It's wonderful," says Hailin Wang, a physicist at the University of Oregon in Eugene who has been working on a rival technique for putting an oscillator into the ground state. The work shows that the laws of quantum mechanics hold up as expected on a large scale. "It's good for physics for sure," Wang says.
So if trillions of atoms can be put into a quantum state, why don't we see double-decker buses simultaneously stopping and going? Cleland says he believes size does matter: the larger an object, the easier it is for outside forces to disrupt its quantum state.
"The environment is this huge, complex thing," says Cleland. "It's that interaction with this incredibly complex system that makes the quantum coherence vanish."
Still, he says, there's plenty of reasons to keep trying to get large objects into quantum states. Large quantum states could tell researchers more about the relationship between quantum mechanics and gravity--something that is not well understood. And quantum resonators could be useful for something, although Cleland admits he's not entirely sure what. "There might be some interesting application," he says. "But frankly, I don't have one now."
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4 Comments
Add CommentLong before Dr. Cleland's experiment Dr. Oscar Mur, prof. at Boston U., had demonstrated the equivalent possibility by using a 'special' motor transferring particles against their concentration gradient. It was part of his doctoral thesis at MIT. Dr.d
Reply | Report Abuse | Link to thisA Simpler Approach: Energy, can be leveraged by way of natural forces, (Gravity, Electrostatics, and Magnetism) to generate more energy that is required to generate such energy. In other words, "continuous motion" is possible. Not by way of matter converted into energy, but by energy generating itself via a gear-ratio through a mechanical format, based on natural and free energy, save the second law of thermodynamics, which will produce entropy, or in simpler terms atrophy in time of the mechanical parts.
Reply | Report Abuse | Link to thisFusion, wormholes, and the like are the great pursuits of our time and the future, but they require energies, to date that are unrealistic to manifest a practical result. If the world of physics would work within the scope of these natural forces, both within the quantum and realtive worlds, we could synchronize, and build a common ground for improving the entire world both socially and technically, through the leadership provided by technology. If you have any further interest, see my blog site and articles on this subject: www.otterwrite.blogspot.com Obviously, I do dream, but I have given a life time of thought to these ideas, since I was a young child. I do hope someone finds them of interest. My perspective may seem navie to many, but given some time to reflect on these ideas and the mechanics involved, it all seems, not only possible, but boundless. Thank you for this response format, Russ Otter
Cleland says the resonator is "essentially still" when phonon quantized vibrational energy exists in discrete packets of quanta vibration as the ultimate indivisible quanta of vibration. Is this really the absolute unit of energy, or just the smallest amount discovered? and who can say what or where is the ultimate vacuum energy of the universe where this so called vibration stillness exists for everything? Seems smaller particles undermining and responsible for the existances of larger objects causes the spookiness and dual possible outcomes (vib/not vib), and has nothing to do with the differences between quantum and cosmic scales? Early objects of huge sizes and masses in the universe like quasars behave like giant accelerated particles.
Reply | Report Abuse | Link to this"And quantum resonators could be useful for something, although Cleland admits he's not entirely sure what. "There might be some interesting application," he says. "But frankly, I don't have one now.""
Reply | Report Abuse | Link to thisI seem to remember that the then king of England,George V (?) on being shown an experiment using electricity asked "But what use is it?" The experimenter replied something like,"l don't know but l'm sure you can tax it"