Posted on 10/30/2006 7:29:53 PM PST by annie laurie
Building upon recent studies on optomechanical entanglement with lasers and mirrors, a group of scientists has developed a theoretical model using entanglement swapping in order to entangle two micromechanical oscillators. This ability could lead to advances in information processing, as well as other applications that use micromechanical resonators, such as electrometers, displacement detectors, and radio frequency signal processors, wrote scientists Stefano Pirandola et al. in a recent Physical Review Letters.
"Until now, entanglement has been observed only for optical modes, i.e., photons (which are massless particles)," Pirandola told PhysOrg.com. "The significance of purely mechanical entanglement would be that it involves massive objects like mechanical oscillators (small vibrations on a mirror). Even though the oscillators must be small--their mass should be on the order of micrograms and their length around the micrometer--these sizes are 'macroscopic' for a quantum mechanical object."
The two entangled oscillators in Pirandola et al's proposed model are the mechanical components of two separate micro-opto-mechanical systems. Instead of entangling the oscillators directly, the scientists suggested entangling the optical parts of the systems--the reflected laser beams--and then used entanglement swapping to correlate the two oscillators.
In entanglement swapping, two objects that have correlated properties never meet directly; instead, a third party acts as a messenger between the two, swapping their properties as accurately as if they had directly interacted. One potential use for entanglement swapping is in quantum repeaters for future quantum computers, which would amp up the signal over long distances to prevent it from being buried by noise and dying out.
Earlier studies on optomechanical entanglement (extensively performed by the Univ. of Camerino group) demonstrated that radiation pressure from an intense laser beam shining on an oscillator could excite the oscillator's vibrational mode and yield two optical sideband modes induced by the vibrations. In the current scheme, when the two oscillators are positioned in such a way that their generated optical modes meet after reflecting, the beams could be mixed with a beam splitter.
Next, a "middleman" detection device would detect and mix the optical modes, and also perform measurements such as joined Homodyne detections, which are standard optical measurements for detecting radiation. When the detector performs these measurements, it can pass on the outcomes of the measurements to both the oscillators. Through this swapping, the entanglement changes from optomechanical to purely mechanical.
In addition to opening the doors to future applications, mechanical macroscopic entanglement would also demonstrate that mechanical systems made of atoms can exhibit quantum behaviour. Pirandola et al's calculations for quantum entanglement on a macroscopic scale, in a purely mechanical state, suggest that quantum phenomenon may not be as limited to the quantum world as scientists once thought.
"Would this theoretical scheme diminish the differences between the macroscopic and quantum worlds? This is a fundamental question of quantum mechanics," said Pirandola. "Whether or not there is a maximum size for oscillators that demonstrate entanglement is an open question right now. We don't know if there is some limit for the sizes of the objects to be entangled. Optimists think that it is only a matter of advances in quantum technologies."
Citation: Pirandola, Stefano, Vitali, David, Tombesi, Paolo, and Lloyd, Seth. "Macroscopic Entanglement by Entanglement Swapping." Physical Review Letters. 97, 150403 (2006).
Really tiny big stuff.
Cool.
Just be careful to keep this within the U.S. The Founding Fathers warned against foreign entanglements...
[...running...]
;-)
They've just discovered Willie Nelson's beard?
I am certainly no expert, but my understanding is this: the "teleportation" phenomenon has been demonstrated, while the experiment in the above article is still in the theoretical stage. The former was done with photons, the latter with mechanical (massive) objects (massive on a quantum scale, that is ... we're not talking about elephants or anything ;-))
I will defer to a more knowledgeable Freeper to correct me if I'm in error :)
If I could just get the tangles out of my hair after washing ...
I didn't do a good job of explaining it, but here's a more detailed article (you can see what I mean regarding the photons):
http://www.spaceref.com/news/viewpr.nl.html?pid=20993
Based on a reading of the spaceref article in post 13, the two seem somewhat different to me (both in apparatus and process). Hopefully a more knowledgeable person than I will come by later tonight or tomorrow, and let me know if I'm right or wrong in my conclusion :)
I'm out for the evening, I'll check back tomorrow to catch up.
Take care :)
Ah yes. Years ago I knew that an optical computer would arrive sooner or later. With 10011001 digital computing you have nothing more than the dit-dah-dit of morse code, flicking a light switch on and off at ever higher speeds; really quite primitive. With millions of discernable light wavelengths as pixels instead of 0,1 bits, and photons are 1000 times faster than slowpoke electrons...that represents a true quantum leap forward in computing. Memory storage? Slow light. Now comes entangled mirror elements, possible switching units. Yup, it's all coming together : a LIGHT computer that is so fast and powerful that it will be AI, but remember the TERMINATOR movie too...
Disclaimer: Opinions posted on Free Republic are those of the individual posters and do not necessarily represent the opinion of Free Republic or its management. All materials posted herein are protected by copyright law and the exemption for fair use of copyrighted works.