# Quantum State of Cards

1. Jun 8, 2015

### Jim Frank

I can understand that the state of a particle
is not known or even determined until it is viewed. What about a deck of cards that have been thoroughly shuffled and not looked at. Can the top card take on the value of any card before they are looked at or are they set at the time they are shuffled.

I understand that the wavelength of the card deck is quite a bit different that the wavelength of an electron so the quantum effects might not apply.

Any thoughts?

2. Jun 8, 2015

### Orodruin

Staff Emeritus
The top card most certainly is fixed even before you have looked at it. Quantum effects do not occur at the scale of cards.

However, if the deck is well shuffled, the probability of the top card being any particular card is well described by 1/52, but this has more to do with your assumption that the deck is well shuffled.

3. Jun 8, 2015

### Jim Frank

So the quantum effect is due to the size of the cards? It works on electrons but a card deck is too large. I understand, Thanks for your assistance.

4. Jun 8, 2015

### meBigGuy

I just want to state my view to see if it is in line with what the experts think. (not a pet theory, just my understanding)

Roughly, Things can have superpositions of states at scales where they are not interacting a lot with other things. A particle can have a superposition of states until it interacts with something that measures/observes it, or otherwise forces it to take a state (decoherence). The concept is "interaction in a thermodynamically irreversible way".

At the scale of cards, the cards are interacting with the atmosphere, other cards, your fingers, etc. The ink is interacting with the paper, etc etc. Simply put, there is no possibility of multiple states at the scale of the cards that would fulfill all the conditions of all those interactions.

5. Jun 8, 2015

### StevieTNZ

In principle QM applies to macroscopic systems. Decoherence is simply entanglement with the environment. Decoherence does not produce a "classical state". It looks like we may have classical reality, but that is because we have not specified all the information of the environment (we get a density matrix).

6. Jun 8, 2015

### meBigGuy

I thought that decoherence indicated that one has pretty much pinned down the relationship between a thingy and its entangled environment. It appears like a classical state, but there is no such thing as a classical state (if you are accepting no-collapse decoherence). At the scope of a card in a deck, with all its physical uniqueness, it would be difficult for it to be so independent of its environment so as to be a superposition of two or more cards. That becomes the difficulty of producing detectable QM effects in macroscopic systems.

7. Jun 8, 2015

### StevieTNZ

I don't think it that would be the case - the card would be a superposition of two or more cards (if that is a prediction of the fundamental Schrodinger equation) while entangled with the environment

8. Jun 9, 2015

### meBigGuy

I did say difficult, meaning highly improbable. I didn't mean to imply impossible. Are you disagreeing with that?

9. Jun 11, 2015

### StevieTNZ

I don't understand what you are asking. What are you referring to as difficult? If its about the cards being in superposition, I've answered that. If its about detecting macroscopic quantum effects, I didn't address that part of your post.

10. Jun 11, 2015

### meBigGuy

What you said: If the Schrodinger equation for the system says they are in superposition while entangled with the environment, then they are (obviously).
I'm just saying that achieving that superposition in the lab would be "difficult", an unscientific subjective judgement. Are you saying that it would not be "difficult"?
I didn't think I was saying anything controversial. So maybe I'm not understanding some nuance of what you are saying.