Physicists Show Theory of Quantum Mechanics Applies to the Motion of Large Objects

Mar 17, 2010
a, Scanning electron micrograph of a suspended film bulk acoustic resonator. b, Fundamental dilatational resonant mode for the mechanically active part of the resonator. The thickness of the structure changes through the oscillation cycle. c, Equivalent lumped-element circuit representation of the mechanical resonator, based on a modified van Dyke-Butterworth model. d, Measured classical transmission, |S21| (blue), and fit (red) of a typical mechanical resonance. (See original research paper for details) Image credit: Nature.

( -- Researchers at UC Santa Barbara have provided the first clear demonstration that the theory of quantum mechanics applies to the mechanical motion of an object large enough to be seen by the naked eye. Their work satisfies a longstanding goal among physicists.

In a paper published in the March 17 issue of the advance online journal Nature, Aaron O'Connell, a doctoral student in physics, and John Martinis and Andrew Cleland, professors of physics, describe the first demonstration of a mechanical resonator that has been cooled to the quantum ground state, the lowest level of vibration allowed by quantum mechanics. With the mechanical resonator as close as possible to being perfectly still, they added a single quantum of energy to the resonator using a (qubit) to produce the excitation. The resonator responded precisely as predicted by the theory of quantum mechanics.

"This is an important validation of quantum theory, as well as a significant step forward for nanomechanics research," said Cleland.

The researchers reached the ground state by designing and constructing a microwave-frequency mechanical resonator that operates similarly to -- but at a higher frequency than -- the mechanical resonators found in many cellular telephones. They wired the resonator to an electronic device developed for quantum computation, a superconducting qubit, and cooled the integrated device to temperatures near . Using the qubit as a quantum thermometer, the researchers demonstrated that the mechanical resonator contained no extra vibrations. In other words, it had been cooled to its quantum ground state.

The researchers demonstrated that, once cooled, the mechanical resonator followed the laws of . They were able to create a single phonon, the quantum of mechanical vibration, which is the smallest unit of vibrational energy, and watch as this quantum of energy exchanged between the mechanical resonator and the qubit. While exchanging this energy, the qubit and resonator become "quantum entangled," such that measuring the qubit forces the mechanical resonator to "choose" the vibrational state in which it should remain.

In a related experiment, they placed the mechanical resonator in a quantum superposition, a state in which it simultaneously had zero and one quantum of excitation. This is the energetic equivalent of an object being in two places at the same time. The researchers showed that the again behaved as expected by .

Explore further: Better thermal-imaging lens from waste sulfur

More information: Quantum ground state and single-phonon control of a mechanical resonator, Nature advance online publication 17 March 2010; doi:10.1038/nature08967

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3.3 / 5 (3) Mar 17, 2010
So when can we expect entanglement and quantum teleportation for macroscopic objects?
not rated yet Mar 17, 2010
Were those rogue waves not already an example of this?
not rated yet Mar 18, 2010
So maybe in some time they will entangle photon with a cat?
If there is also a person in such isolated system, he will know the state of the cat, while for outside observer they will be in superposition...
Wait - there are no isolated systems!
Really? What about spatial separation - if they are on a colony a light year away - for at least a year after cat's death, for us they still will be 'in superposition'...
not rated yet Mar 18, 2010
Such looking natural tool to work with situations we don't/cannot have full information is believed to be fundamental - that these subjective descriptions cannot be joined into objective picture - because quantum correlations doesn't fulfill Bell inequalities.

But situation changes when we assume determinism, e.g. governed by some Lagrangian - from our perspective of time it's equivalent with Einstein's block universe - static 4D picture.
In this case even the simplest stochastic model - uniform distribution among trajectories has correlations not fullfilling Bell's inequalities, but 'quantum' - with 'squares' - PHYSICS CAN BE OBJECTIVE!
not rated yet Mar 18, 2010
Single-particle interference was already observed for macroscopic objects:

not rated yet Mar 18, 2010
I also read about Nano-transport []

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