Quantum cats, or, Generation of Optical Coherent State Superpositions by Number-Resolved Photon Subtraction from Squeezed Vacuum
September 2, 2010 12:23 AM   Subscribe

 
Also, Science Daily.
posted by twoleftfeet at 12:33 AM on September 2, 2010


Dibs on this as my bandname. The Quantum cats. We'll be playing rockabilly at high speeds.
posted by dabitch at 2:15 AM on September 2, 2010


after Nobel Prize winner Erwin Schrödinger who theorized cats existed in both alive and dead states

If there's one thing I hate, it's zombie cats. The other thing I hate is science journalists who could do better.
posted by hanoixan at 2:19 AM on September 2, 2010 [11 favorites]


In 2005 NIST scientists said they coaxed six atoms into spinning together in two opposite directions at the same time.

Science just doesn't even make any fucking sense anymore.
posted by valrus at 4:23 AM on September 2, 2010 [4 favorites]


Next: Quantum LOLCATS, which exist in a superposition of haz cheezburger and haz no cheezburger.
posted by Johnny Assay at 4:44 AM on September 2, 2010 [20 favorites]


Ok, after 45 minutes and 1.5 cups of coffee I'm going to take a potentially embarrassing stab at this and hope someone with a better understanding will be kind enough to help me understand if I am mistaken or tell me if I'm close:

This is about 2 things. We have now observed the previously theorized existence of photons in a quantum state. We are able to generate and then observe with more accuracy the quantum states of small sets of photons than we can by generating and observing the quantum states of single photons. This increased accuracy is beneficial in the endeavor to produce quantum computers.

I now have a quantum headache.
posted by vapidave at 4:58 AM on September 2, 2010


Wait a second.... I thought observation collapsed the quantum superposition. So how can we observe a superposition? Somebody who actually studies this stuff, please help. =]
posted by yeolcoatl at 5:14 AM on September 2, 2010


So is it true that everyone is either a quantum cat or a quantum dog person?
posted by arcolz at 5:15 AM on September 2, 2010 [1 favorite]


Quantum Cats is one of the strangest sites I've seen in some time. I have no idea how these people got their cats squeezed into their vacuum, or why.

hahahahahahahahaha! I had to post that!
posted by Multicellular Exothermic at 5:17 AM on September 2, 2010 [7 favorites]


Do they sleep 20 hours a day and shed quarks all over your clothes?
posted by tommasz at 5:21 AM on September 2, 2010


So is it true that everyone is either a quantum cat or a quantum dog person?

Only when observed. When you're alone in your box you can be both simultaneously.
posted by condour75 at 5:24 AM on September 2, 2010 [3 favorites]


It had to be done.
posted by Splunge at 5:26 AM on September 2, 2010 [2 favorites]


Call me when they've made quantum beer.
posted by EndsOfInvention at 5:42 AM on September 2, 2010


after Nobel Prize winner Erwin Schrödinger who theorized cats existed in both alive and dead states
I have in fact seen alive cats and I have seen dead cats, so this isn't just crazy talk. That Erwin came up with some damn fine theories, right up there with Anne Elk.
posted by Killick at 6:05 AM on September 2, 2010 [2 favorites]


So are these the cats that the internet is made of? That would explain the optic cables.
posted by maryr at 8:03 AM on September 2, 2010


It's hard to take a website seriously when, right in the middle of their article, the text is interrupted to link me to "15 genius algorithms that aren't boring".

Yeah, I hate being bored while reading science! That's why I spend most of my time playing football and giving people wedgies instead. I'll just get some nerd to do my science homework for me.
posted by Galaxor Nebulon at 8:05 AM on September 2, 2010


In 2005 NIST scientists said they coaxed six atoms into spinning together in two opposite directions at the same time.

Science just doesn't even make any fucking sense anymore.


No, the math is fine. Your problem, and it's a real one, is that the analogy used in QM is broken.

A QM particle is hard to picture. It has a number of separate attributes that fit into theory in particular ways, charge and mass are common ones, but "spin" is another. Pauli first described the math to explain the experiments by others in the 1920s. Shortly after, a bunch of folks ( Kronig, Uhlenbeck, Goudsmit and Dirac) noticed that Pauli's math was pretty close to the way spinning balls are mathematically described, so they called this new attribute of quantum particles "spin".

It's an analogy. It isn't perfect, but it allows us to talk about other attributes (called observables) of quantum particles as well: there's an analogue of angular momentum which is a very convenient way for talking about atomic, molecular and nuclear particle interactions. For example, our explanation for why somethings are blue and others are orange relies on spin and angular momentum.

The problem with the analogy is that QM particles can do stuff that classical billiard balls cannot. Being in an unresolved, "superposed" state is one of them. QM balls can spin in multiple directions at once. At least, that's the way the math works. The observation in 2005 was a neat confirmation of that.

With QM, you have to keep the knowledge that reality isn't the same as the pat analogies. The analogies often are useful for understanding what QM particles do, but you can't take them too seriously.

Part of learning QM is learning to distrust your gut. Things like this bite you in the behind all the time.
posted by bonehead at 8:15 AM on September 2, 2010 [3 favorites]


Misleading article at networkworld.com is misleading. The writer apparently looked at the paper's synopsis at arxiv.org, didn't understand it, and wrote a synopsis about that.

"Schrodinger's cat state" is now used by physicists to refer to a superposition of highly distinguishable states, or "coherent state superpositions" (CSS).

"Schrodinger's cat" refers to the thought experiment proposed by Schrodinger: Put a cat in a box with a lethal trigger controlled by radioactive decay where one particle has a 50% chance of changing quantum state, and you'll have a cat that's indeterminately dead AND alive, unknown by the observer until the act of observation. This is different than CSS.

Schrodinger used the cat example to show the absurdity and incompleteness of quantum theory, not to say that the cat was literally both dead and alive until observed. This point is usually popularly misunderstood.

...yeah, yeah, you knew this already...
...pedant post is pedantic...
posted by lothar at 8:31 AM on September 2, 2010


lothar, not pedantic at all. I appreciate the distinction. The whole Schrodinger's cat thing has nagged at me a long time. This thread has helped me understand that the language used is really jargon, where attributes described most certainly do not do what they say on the tin.
posted by Xoebe at 12:14 PM on September 2, 2010


bonehead: Wow, thanks for the thoughtful reply to my wiseass one-liner! It made sense to me, as much as anything in QM does. My own background is in math, and it seems like the closest analogue (that I'm aware of) there is when you start throwing out properties of algebraic structures, like commutativity in groups or unity in rings, and seeing what you can still conclude; mostly because when you do that, your long-held notions about how math works can really lead you astray.

Do you have any good resources on quantum mechanics for someone with a math background? I recently read A Brief History of Time and felt like Hawking had to skirt around a lot of the meat in order to keep it accessible.
posted by valrus at 2:56 PM on September 2, 2010


"Wait a second.... I thought observation collapsed the quantum superposition. So how can we observe a superposition?"

Not a scientist, but my understanding is that the superposed states interact with each other, so what you look for is evidence of that interaction, rather than observing the "cat state" directly.

For a really simple example, look at the double slit experiment. Electrons shoot through two slits and form an interference pattern on a screen. You can't see the superposition where the electron is both particle and wave (since that would collapse the electron's state, like you said), but the pattern on the screen indicates that both states must have occurred simultaneously, since particles would just form two separate lines as they came out of the slits.
posted by Kevin Street at 3:20 PM on September 2, 2010


In this experiment the evidence of interaction between different states would appear to be an alteration in the electric field values for the photons, as is suggested by the picture in the Science Daily article.
posted by Kevin Street at 3:46 PM on September 2, 2010


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