Thursday, March 18, 2010

Micron Size Quantum Object

An amazing feat of accomplishment here in this experiment. A group at UC-Santa Barbara has made a quantum oscillator the size of a 0.0002 millimeter-square wafer[1]. You can read a review of this work at Wired Science.

The mechanical object used in the experiment, published March 17 in Nature and led by Cleland and fellow UCSB physicists John Martinis and Aaron O’Connell, is a 0.0002 millimeter-square wafer of quartzlike material bracketed by metal plates. The wafer is a piezoelectric resonator, expanding and contracting in response to electrical voltages at a precise, extremely high frequency. Cleland likened its expansion and contraction to the inflation and deflation of a balloon.

The quantum device is a qubit, a term that generically refers to a kind of quantum transistor being used for quantum computation, in this case made from an ultrathin aluminum-based superconductor. At extremely cold temperatures, it goes quantum: It exists in an oscillating waveform spanning an excited state, an unexcited state, or both simultaneously, all controlled by electrical currents.

So we are beginning to see larger and larger sizes of objects exhibiting clear quantum mechanical behavior. However, note that, even though by quantum standards, these are "large" objects, they are still minuscule by our everyday scale. Yet, look at all the trouble they have to go through to be able to make such a size behave quantum mechanically. The cooling process to get it into its lowest quantum state is not trivial. We have to do that so that we CAN detect clearly the quantum behavior. It is not that easy to detect such behavior for large objects, and think of how difficult it is to detect quantum behavior from an object the size of a ping pong ball!

The points in all of this is that, to see quantum behavior in macroscopic objects at the macroscopic scale, one has to put the system into a very spacial situation. It makes it extremely difficult to see quantum effects at such a scale. This is one important point that pseudoscientists and crackpots have overlooked when they bastardize quantum mechanics. People like Deepak Chopra and The Secret used QM to justify their beliefs, but they somehow missed the fact that at the macro scale, the quantum effects predominantly unobservable. We continue to make baby steps at constructing larger and larger system that can exhibit quantum behavior, but these systems are very difficult to construct and requires a lot of "hoops" to jump through. So to declare that some human behavior or human consciousness can be described via a principle that can be explained using quantum mechanics is totally unjustified and unverified. It has no empirical basis at all.


[1] A. D. O’Connell et al., Nature advance online publication 17 March 2010 (exact reference will be posted when it is published).

1 comment:

Anonymous said...

Is this a "pure" or "mixed" quantum state? That is, is the density matrix just

rho =|psi><psi|

or is it a weighted sum of such products?

Do not SQUIDs exhibit this same quantum behavior?