Physics education research, electronic materials, and the musings of Christopher Moore, Ph.D.

Thanks to Roger Penrose for this one!

Say we need to safely transport a quantum object from one place to another but the conditions have become far to ‘noisy’ for the trustworthy transportation of a quantum object or quantum signal of any kind. We are only allowed to transmit classical information. However, it is impossible to transmit a quantum state using only classical signalling because classical signals can be copied and the coping of a quantum state is impossible. Suppose I have a colleague working on Saturn’s moon Titan. Now, suppose that several years ago we each took possession of one member of an EPR pair of particles of spin ½. We can suppose that the particles started together in a state spin of 0. Our supposition is that it is now unreliable to send quantum states across the reaches of space between Earth and Titan. But, let us say that, several years ago before my colleague left for Titan, we each took our respective particle of the aforesaid entangled pair and each particle was kept perfectly isolated from external disturbance, so that if they were brought together again the state spin would be 0.  Now, suppose that another friend of mine on Earth presents me with another particle of spin ½, again kept isolated from external disturbance. I am asked by my friend to transmit the state spin of his particle, intact, to my colleague on Titan right away. I am only allowed to send a classical radio signal to my colleague on Titan. How would I go about completing my task considering the conditions mentioned above? Good luck! Cheers.

Last edited by threequarksforme (2005-07-26 01:40:21)