Naked Science Forum
Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: thedoc on 06/12/2011 13:37:55
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This week, researchers from the UK, Canada and Singapore have accomplished quantum entanglement on the macro scale, entangling two millimeter-sized diamonds.
Read the whole story on our website by clicking here (http://www.thenakedscientists.com/HTML/content/news-archive/news/2445/)
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fractal geometry in forest?psychic entanglement of biotwins? clone might do better?
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This week, researchers from the UK, Canada and Singapore have accomplished quantum entanglement on the macro scale, entangling two millimeter-sized diamonds.
Read the whole story on our website by clicking here (http://www.thenakedscientists.com/HTML/content/news-archive/news/2445/)
[chapter podcast=3748 track=11.12.04/Naked_Scientists_Show_11.12.04_9402.mp3](https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fwww.thenakedscientists.com%2FHTML%2Ftypo3conf%2Fext%2Fnaksci_podcast%2Fgnome-settings-sound.gif&hash=f2b0d108dc173aeaa367f8db2e2171bd) or Listen to the Story[/chapter] or [download as MP3] (http://nakeddiscovery.com/downloads/split_individual/11.12.04/Naked_Scientists_Show_11.12.04_9402.mp3)
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So what created that entanglement?
The durations of the laser?
Thanks for the explanation though, what I've seen of it before made no sense, but this do. So they took two diamonds, of a same inner structure, and size and mass too? Then they induced energy, by a laser, in both, using two short 'pulses' at each diamond simultaneously.
If the system, the two diamonds now was defined as, was 'classical', then you shouldn't expect the second pulse to become stronger as it passed through the diamond into the detector more than half of the times, that as 'classically' the energy is expected to be 'localized' to the spot where the laser hit it?
How do they define it? If you impart a momentum, why shouldn't it spread through the whole diamond every time you do it, why only half of the time?
Because of the pulses short durations apart limited each photons momentum spreading inside the diamond? Or is there something more to it, can you define it as them not losing any energy, other than in the direction of their motion?
But accepting the definitions/assumptions there seems a entanglement, as all secondary pulses had more energy when detected.
In this case, are we talking of waves or photons btw?
"They fired two laser pulses at each diamond, 350 femtoseconds apart." which are quite long. 1000 times longer than 350 attoseconds if I got it right? And we've got down to 12 attoseconds measuring, so would that be measure as photons or waves?
They seem to treat it as photons though? So how did they define that, through the detector?
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Ahh okay, ( 350 femtoseconds apart) but what was the duration of the lasers firing? Somehow it feels as 'scales' plays an important role here :)
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Hmmm,
I am still a bit lost with what they actually did, and most of the article is stuck behind the PayWalls.
Here is the main figure:
(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fwww.sciencemag.org%2Fcontent%2F334%2F6060%2F1253%2FF1.large.jpg&hash=86653ff24091058e6ffb8971c048db6c)
Fig. 1
Schematic of the experimental layout for generating entanglement between two diamonds. A pump pulse is split by the beamsplitter BS and focused onto two spatially separated diamonds. Optical phonons are created by spontaneous Raman scattering, generating the orthogonally polarized heralding Stokes fields sL, sR [see inset (A): |n〉 represents phonon number states in diamond]. Polarization beamsplitter PBS1 combines the spatial paths, and the half-wave plate HWP rotates and mixes the fields on PBS3, which are then directed into the single-photon detector Ds. A probe pulse, with programmable delay, coherently maps the optical phonon into the orthogonally polarized anti-Stokes fields aL, aR [see inset (A)], which are similarly combined and mixed on PBS2 and PBS4, and detected on the detectors Da+, Da−. The relative phase ϕa between the fields aL,R is controlled by a sequence of quarter- and half-wave plates (18). Rejected pump beams from PBS1,2 are used to stabilize the interferometer. Displacements of neighboring atoms from their equilibrium positions are anticorrelated in the optical phonon mode [see inset (B)], with a vibrational period of 25 fs in diamond. Inset (C) shows one of the diamond samples, with a coin for scale.
Diamonds are an interesting choice because light can be reflected internally, perhaps that accounts for some of the priming between pulses.
Anyway, is it the diamonds that are entangled, or the light pulses?
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Very nice question Clifford. Depends on how you look at it I guess :) I would say that they define it as it is the diamonds that now are entangled. The problem might then be that if they are, the entanglement then should cover the whole of the system? Meaning that this light pulse/photons sent that somehow not is expected to disperse into the whole of the diamond(s) under the firings, later, when looked at the whole experiment yet..Is expected.. to cover the same whole that earlier was treated as 'pinpointing'?
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You might want to look at it as a result of 'wave functions'. Then the diamonds disappear, instead you have a mathematical equation symbolizing the 'system'. In the case of before firing you then will have two wave functions describing each one of the diamonds (ignoring laser etc). After the firing the diamonds represent one same wave function mathematically if entangled. That is on a theoretical plane though, not considering that those diamonds actually is there at all times.
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Ahh sweet, they split the light in a beam splitter, so the light hitting the diamonds are/is already entangled :) as it has a same origin. Then what you do to one 'side' of the 'wave function' that this light (now split into two parts but still being one wavefunction) represent should be reflected in the other 'side'.
Ouch, that is wrong, splitting the light the definition is that you can deflect one of its two paths without changing its common 'wave function', so what I should mean here is the final measurement. And as always that gives me a headache. How can we change its path without interacting? Only if assuming 'fields' and that the 'field' also is what creates the entanglement, maybe??
So maybe I'm wrong there, maybe they don't define it as the diamonds that are entangled?
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It becomes slightly weird, in that if I assume that they do mean that the diamonds now are 'entangled' as a whole 'wave function' then it seems to me that I can do this same thing on my cup and telly too? Which then by definition should mean that they too becomes entangled. Assuming that what 'entangles' is the light/photons? Or is this only expected in Raman-active media like a diamond?
Why?
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http://www.scientificamerican.com/article.cfm?id=room-temperature-entanglement
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Very nice Czarcar.
"But because of the experimental design, there is no way of knowing which diamond is vibrating. "We know that somewhere in that apparatus, there is one phonon," Walmsley says. "But we cannot tell, even in principle, whether that came from the left-hand diamond or the right-hand diamond."
In quantum-mechanical terms, in fact, the phonon is not confined to either diamond. Instead the two diamonds enter an entangled state in which they share one phonon between them."
So it is the setup of the experiment that defines it. But it still doesn't answer the question if I can 'entangle' my cup with my telly this way? If the definition craves for the experimenters not to 'know' the specific locations of from where those vibrations come, then it is highly mystical :) from a classic perspective.
Then again, assuming that this is right everything can, and ultimately will, be entangled, assuming that you don't know, right :)
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Well defining it as 'phonons' vibrating in a lattice you can entangle about anything with anything using split light, but I don't know if you can say that is is the whole of the diamonds that now are entangled? Only if assuming that this vibration is 'existing' in the whole of the diamond as it seems to me? But defining it as a shared wave function then?
If I do define it that way it seems to me that I'm also stating that the macroscopic 'diamonds' must 'vibrate/resonance' with that phonon, am I right? And that makes me wonder if you can thread a 'entanglement' on a 'entanglement' resonance wise? Weird idea, but it's been on my mind.
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What I mean here is that for a single particle there may, depending on how you create the entanglement, be one or more particles it is entangled too. But for a macroscopic diamond, described by those particles, the 'vibrations' should become a composite, making it entangled through the universe, maybe :) eh, possibly, etc ::))
As I said, it's a really weird question/idea.
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I do like it though. and using that idea as a argument for the 'size' of something? I can now eh, 'state' that with all particles existing, finding one entanglement per particle, I halved the universes 'size'. Assuming that macroscopically all objects are 'coupled' through entanglements, to all other objects, then our macroscopic universe has no 'size' at all :)
Which is very weird, so a better choice would be to assume that as all 'particles' comes from a Big Bang in the mainstream definition, they should all be entangled to all other particles, from the universes very beginning.
Which leaves you to define how a entanglement is 'broken'.