NIST Physicists Coax Six Atoms Into Quantum 'Cat' State

Science Daily | National Institute of Standards and Technology ^ | 2005-12-03

[VadeRetro]

In addition, cat states are more sensitive to disturbance than other types of superpositions, a potentially useful feature in certain forms of quantum encryption, a new method for protecting information by making virtually all eavesdropping detectable.

This works in a cool way. You basically send your message via pulses of cat-state particles of which each is entangled with a particle you are NOT sending. If the cat-state of your stay-at-home particles collapses too soon, some eavesdropper has sensed your message along the way.

[Doctor Stochastic]

This stuff reminds me of the square root of -1--it shouldn't exist but it is a useful tool in the real world.

Why shouldn't it exist? I would imagine that it's as real as any other number. (Note the complex sentence.)

The real question (IMNSHO) is: "Why does the Sqrt(-1) suffice?" In other words, why do we not need CubeRoot(-1), etc.?

[King Prout]

I'm thinking that should be "10^26 atoms"
otherwise, interesting indeed.
I agree with Einstein: entanglement IS spooky.
I cannot help but wonder whether entanglement might lead to instantaneous communication over practically infinite distances.
corollary: if it can, then I cannot help but think that perhaps the SETI folks have been barking up a very wrong tree in listening for alien radio comsig.

[Physicist]

It's not that the cat IS both alive and dead, it's that we can't know which is true. We can only know the probability of the event being true. Only by actual observtaion is the actual state know and then it becomes one or the other.

That's not correct. The two states are simultaneously "real" at the 50% level. Quantum superposition is a statement about reality, and not only about our knowledge of reality.

Einstein shared your misconception, and insisted that the two would be experimentally indistinguishable in any case. After his death, however, it was discovered that he was wrong: indeterminate states behave differently from merely undetermined states. The latter will obey Bell's Inequality when you compare correlated measurements; the former will violate it.

The experimental fact is that entangled states yield measurements that violate Bell's Inequality.

[js1138]

Doesn't work that way. You can't send information faster than light.

[Physicist]

Regarding the 1026 issue:

Here is the original press release. You can see that the "26" is superscripted. The "1026" was a copy-and-paste job from the original, nothing more.

[King Prout]

are you sure?
last I checked - the US/German experiment - the implication was instantaneous mirroring of changes irrespective of distance.

[js1138]

I'm just mirroring what I've read. The technique sounds impressive when written about, but I'm pretty sure it doesn't allow communication faster than light.

[King Prout]

I'll be the first to admit I'm not even at piker-comprehension concerning QM, so all of this is like nifty sorcerous lunacy to me.

[Servant of the 9]

The name was coined in a famous 1935 essay in which German physicist Erwin Schrödinger described an extreme theoretical case of being in two states simultaneously, namely a cat that is both dead and alive at the same time.

Schrödinger obviously never drank tequila or he would know an entire human body can enter a cat state on any given morning.

So9

[Servant of the 9]

Doesn't work that way. You can't send information faster than light.

Not in classical or relativistic physics you can't, but there are some questions in quantum physics.
Electrons do not move from one orbit to another of an atom, but disapear one place and appear instantaneously in another orbit. There are a nuumber of other quantum transitions that take place without passage of time.
Is information moved? That is the difficult quible.

So9

[longshadow]

The real question (IMNSHO) is: "Why does the Sqrt(-1) suffice?" In other words, why do we not need CubeRoot(-1), etc.?

Point of Information: do you mean "why do we NOT need CubeRoot (-1), etc." in order to model QM, or are you asking the question in a more abstract, purely mathematical sense?

[js1138]

Everything I have read about quantum entanglement suggests it cannot be the basis of faster than light communication.

At the very least it requires you to physically transport the entangled particles to the receiving destination. That pretty much rules out using it to meet alien civilizations.

[RightWhale]

Time is an illusion. So is space. So is causality. As soon as we perceive the universe correctly, distance will be annihilated, as will past and future.

[Servant of the 9]

Everything I have read about quantum entanglement suggests it cannot be the basis of faster than light communication.
At the very least it requires you to physically transport the entangled particles to the receiving destination. That pretty much rules out using it to meet alien civilizations.

Perhaps not interstellar communications, but instantaneous communication across the diameter of an atom has profound implications for the ultimate speed of electronics devices of all types.

So9

[King Prout]

from what little I have comprehended of what little I have read on the subject, the following is the (quite possibly incorrect impression of) property of entanglement which interests me:

2 entangled particles, separated by significant distance.
perturb one of the particles, and the other particle instantly undergoes the same perturbation.

if this is so, one can consider one state of perturbation a zero, and another state a one, thus creating a binary communicator allowing instantaneous -if absurdly simple- data transfer irrespective of distance.

again assuming all the above, and assuming the number of entangled particles can be jacked up to something more useful, then REAL instant datacomm is possible. the applications would of course include controlling long-range unmanned recon on Earth and (more importantly) in space... no more long waiting periods between command, execution, and reply - it'd become similar to actually being there in real-time, more like controlling an RC car on your lawn.

That'd be damn nifty... if it is indeed possible

[King Prout]

well, philosophically I can see how that could be true - only problem: we are PART of the illusion, so to transcend the illusion we would have to completely transcend ourselves.

that can wait till I die, I reckon :)

[King Prout]

um, isn't the cube root of "negative one" simply "negative one"?

I mean, -1^3 = -1...

[RightWhale]

Yeah, but information cannot be communicated this way. So near and yet so far. BTW, entropy as it is called in information theory is not the same thing as entropy in thermodynamics, just something with the same mathematical form--there is some confusion about this on FR. They are two different words that happen to be spelled and pronounced the same.

[RightWhale]

Not at all. We create the illusion. There is nothing in nature that requires the illusion. Just as there are no patterns in nature: we create the patterns. That appears to be our job.