# Entanglement as a resource

1. Feb 21, 2009

### sirchasm

Does an Alics-Bob scenario include entropy, and does it increase if they both determine correct states?

What if they don't? Is knowing an entanglement exists an expectation? Is measuring it a probability?

So if there's expectation and probability (or maybe there isn't). is there information (with entropy)?
??

(Hope this isn't too much for the mods here)

2. Feb 21, 2009

### sirchasm

What is the connection between superposition, nonlocality and measurement?

No-one knows, or it isn't worth trying to answer - it's too trivial a question.

Why is entanglement unrelated to cosmology? Does anyone know? (I sure don't)

3. Feb 21, 2009

### cristo

Staff Emeritus
Entanglement is a quantum mechanical phenomenon and, as such, this post is better suited to the Quantum Physics forum. Hence, it was moved.

4. Feb 21, 2009

### sirchasm

Entanglement is also a universal phenomenon. Can we assume that it only 'happens' if we do it (locally)?

What connection is there between entanglement and black holes or the information horizon?

5. Feb 21, 2009

### ZapperZ

Staff Emeritus
This really has no meaning. Even if entanglement is a "universal phenomenon", it cannot be easily preserved! One loses coherence VERY quickly, even with just ONE interaction[1]! In fact, it has been shown the the loss of coherence is faster than the typical statistical decay[2]. It occurs very fast that it's been called an entanglement sudden death!

Zz.

[1] https://www.physicsforums.com/showpost.php?p=1498616&postcount=55
[2] Ting Yu and J.H. Eberly, Science v.323 p.598 (2009).

6. Feb 21, 2009

### sirchasm

Entanglement is a correlation; it gets 'decohered' by the environment, or measurement (these are equivalent 'decoherence' operators, at some scale).

What's the relationship between superposition and entanglement? Are they distinct or does one depend on the other?
Is entanglement just a "static" (time-independent) correlation? A sort of 'bit' stored in a memory, whereas 'dynamic' correlations are the equivalent of reading a bit from memory and processing it?

Decoherence is then just 'noise', in the channel, as it were? We need to use ECC in classical communication, we use QECC in quantum communication - this is (to me) an obvious kind of model.

The "problem" is how we get information into the classical domain - obviously it's already there in CC.

Hence the entropy angle, what is quantum information entropy, is it fundamentally different to classical entropy, or is there (apart from the disconnect between classical/quantum) no real difference. (Why should there be?)