Something like this was used to explain quantum entanglement in a book by Julian Brown called, Quest for the Quantum Computer: A single black box has: an on-off switch, a dial with six positions, one red and one green light, a counter which counts how many times the box was turned on. To operate the box, randomly select any dial position and then switch the box "on". Note which light turns on, red or green. Then switch the box "off". The color of the light that gets turned on is guarranteed to always be completely random. There is a 50:50 chance for either the red or green light coming on, regardless of whether the dial's position was changed or not. Now whenever two such black boxes have been switched "on" the same number of times, they will have the same counter number. Then, they will both show the same color light if their dial positions are the same. But whenever the dial on one of the two boxes is in a position opposite to the position of the dial of the other box, the color of the two box's lights will be different (one will be red and the other will be green). And whenever the dial on one of the two boxes is in a position adjacent to the dial position of the other box, the color of the two box's lights will be the same on average 3/4ths of the time. Two such black boxes can be said to be 'entangled'. Can they be physically manufactured without the ability to send information between them?

Wasn't it Eraser who wrote: >Something like this was used to explain quantum entanglement >in a book by Julian Brown called, Quest for the Quantum Computer: > >A single black box has: > an on-off switch, > a dial with six positions, > one red and one green light, > a counter which counts how many times the box was turned on. >To operate the box, randomly select any dial position >and then switch the box "on". Note which light turns on, >red or green. Then switch the box "off". The color of >the light that gets turned on is guarranteed to always be >completely random. There is a 50:50 chance for either >the red or green light coming on, regardless of >whether the dial's position was changed or not. > >Now whenever two such black boxes have been switched "on" >the same number of times, they will have the same counter number. >Then, they will both show the same color light if their dial >positions are the same. But whenever the dial on one of the >two boxes is in a position opposite to the position of the >dial of the other box, the color of the two box's lights >will be different (one will be red and the other will be green). >And whenever the dial on one of the two boxes is in >a position adjacent to the dial position of the other box, >the color of the two box's lights will be the same on average >3/4ths of the time. > >Two such black boxes can be said to be 'entangled'. > >Can they be physically manufactured without the >ability to send information between them? It's easy to design such a system where adjacent positions give the same colour light 2/3 of the time rather than 3/4. To achieve 3/4, I reckon that you have to have a dial with 8 positions. -- Mike Williams Gentleman of Leisure

On 2007-03-23, Eraser <Eraser@Pencil.Box> wrote: > > > Something like this was used to explain quantum entanglement > in a book by Julian Brown called, Quest for the Quantum Computer: > > A single black box has: > an on-off switch, > a dial with six positions, > one red and one green light, > a counter which counts how many times the box was turned on. > To operate the box, randomly select any dial position > and then switch the box "on". Note which light turns on, > red or green. Then switch the box "off". The color of > the light that gets turned on is guarranteed to always be > completely random. There is a 50:50 chance for either > the red or green light coming on, regardless of > whether the dial's position was changed or not. > > Now whenever two such black boxes have been switched "on" > the same number of times, they will have the same counter number. > Then, they will both show the same color light if their dial > positions are the same. But whenever the dial on one of the > two boxes is in a position opposite to the position of the > dial of the other box, the color of the two box's lights > will be different (one will be red and the other will be green). > And whenever the dial on one of the two boxes is in > a position adjacent to the dial position of the other box, > the color of the two box's lights will be the same on average > 3/4ths of the time. > > Two such black boxes can be said to be 'entangled'. > > Can they be physically manufactured without the > ability to send information between them? > > > It's not possible. Given that A implies B, C, or D, then P(A) <= P(B) + P(C) + P(D). Chance (Light 1 != Light 4) <= Chance (Light 1 != Light 2) + Chance (Light 2 != Light 3) + Chance (Light 3 != Light 4) Which implies 1 <= 1/4 + 1/4 + 1/4 == 3/4 This reasoning shows that two adjacent positions will give the same result more than 2/3 of the time. It is possible to achieve 2/3 by having the device give green on three adjacent numbers, with each choice being used 1/6 of the time. It is possible to achieve 0 by using three alternating positions, each 1/2 the time. It is possible to achieve any value in between by an average of those two methods.